Institute of Acoustics: Acoustics Bulletin May / June 2021

Acoustics Bulletin May / June 2021

Volume 47 No 3 May/June 2021

ISO TS 19488:2021 – Acoustic classiﬁ cation of dwellings Page 32 Avoiding sleep disturbance and minimising carbon emissions through sustainable airport operations Page 38

COVER STORY: The sounds of Mars from NASA’s Mars Perseverance Page 22

Instrumentation corner: How much is our hearing actually worth? Page 50

ACOUSTICS ACOUSTICS

BULLETIN BULLETIN

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Image courtesy of NASA/JPL-Caltech

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ACOUSTICS BULLETIN

Contacts Publisher Juliet Loiselle

Contributions, letters and information on new products to: Nicky Rogers Email: nickyr@warnersgroup.co.uk Tel: 01778 391128

Acoustics Bulletin Volume 47 No 3 May/June 2021

Institute aﬀ airs 5 President’s letter

Features 22 COVER STORY Thoughts on the sounds of Mars from NASA’s Mars Perseverance

6 Engineering Division

8 IOA Diploma during the pandemic

wig pe WARNERS MIDLANDS PIC

30 Obituary – Dr Trevor Hickman

12 IOA response to draft guidance on environmental objectives relating to the Space Industries Act 2018

Advertising: Dennis Baylis MIOA Email: dennis.baylis@ioa.org.uk Tel: 00 33 (0)5 62 70 99 25

32 ISO TS 19488:2021 – Acoustic classiﬁ cation of dwellings

€ Institute of Acoustics

38 Technical contribution – Avoiding sleep disturbance and minimising carbon emissions through sustainable airport operations

18 IOA Early Careers Group

Published and produced by: The Institute of Acoustics Silbury Court, 406 Silbury Boulevard, Milton Keynes, Buckinghamshire MK9 2AF Tel: 0300 999 9675

21 IOA STEM activity

General news 64 IOA Branch news

50 Instrumentation Corner – How much is our hearing actually worth? We subject a range of low-cost meters claiming to meet IEC 61672 to a periodic test to see how well they performed

68 IOA Specialist Group news

69 Industry news

Technical articles review procedure All technical contributions are reviewed by an expert identiﬁ ed by publications committee. This review picks up key points that may need clarifying before publication, and is not an in-depth peer review.

Edited, designed and printed by: Warners Group Publications The Maltings West Street Bourne Lincs

61 Online conference to promote mutual discipline awareness between acoustics and architecture students

62 Complex decision-making processes in planning and development proposals

This publication is printed by Warners 01778 395111

Cover image: Perseverance Hazcam First Drive Our cover image was captured while NASA’s Perseverance rover drove on Mars for the ﬁ rst time on 4 March 2021. One of Perseverance’s Hazard Avoidance Cameras (Hazcams) captured this image as the rover completed a short traverse and turn from its landing site in Jezero Crater.

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Views expressed in Acoustics Bulletin are not necessarily the oﬃ cial view of the Institute, nor do individual contributions reﬂ ect the opinions of the Editor. While every care has been taken in the preparation of this journal, the publishers cannot be held responsible for the accuracy of the information herein, or any consequence arising from them. Multiple copying of the contents or parts thereof without permission is in breach of copyright.

Regular 60 2021 events

70 Institute diary

€ Institute of Acoustics

The Institute of Acoustics is the UK’s professional body for those working in acoustics, noise and vibration. It was formed in 1974 from the amalgamation of the Acoustics Group of the Institute of Physics and the British Acoustical Society. The Institute of Acoustics is a nominated body of the Engineering Council, oﬀ ering registration at Chartered and Incorporated Engineer levels. The Institute has over 3000 members working in a diverse range of research, educational, governmental and industrial organisations. This multidisciplinary culture provides a productive environment for cross-fertilisation of ideas and initiatives. The range of interests of members within the world of acoustics is equally wide, embracing such aspects as aerodynamics, architectural acoustics, building acoustics, electroacoustic, engineering dynamics, noise and vibration, hearing, speech, physical acoustics, underwater acoustics, together with a variety of environmental aspects. The Institute is a Registered Charity no. 267026

Permission is usually given upon written application to the Institute to copy illustrations or short extracts from the text or individual contributions, provided that the sources (and where appropriate the copyright) are acknowledged.

The Institute of Acoustics does not necessarily endorse the products or the claims made by the advertisers in the Acoustics Bulletin or on literature inserted therein.

Annual Subscription (6 issues) £134.00 Single copy £23.00

@2021 The Institute of Acoustics

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LETTER FROM MILTON KEYNES

Dear Member

t was on the 12th March 2020 that the Institute held its last in-person meeting before of the ﬁ rst lockdown occurred. The meeting explored the appetite for revising or replacing the Calculation of Road Traﬃ c Noise and the Calculation of Railway Noise through an initiative by the British Standards Committee on Transportation Noise. The one-day meeting took the form of presentations and a workshop discussion, and was scheduled to be held at the Jurys Inn hotel in Milton Keynes (just over the road from our headquarters). As the date of the meeting approached, concern about COVID was increasing daily. This included some delegates saying that their employer would not permit travel to the meeting because of the risks involved. So, the Institute faced a dilemma – we did not want to cancel the meeting but yet, how were we to engage with those members who wanted to attend but couldn’t? The outcome was a blended meeting using the Zoom facilities we have in the conference room at HQ. The presentations took place there, with about 40 to 50 people attending in person and with about a dozen delegates watching remotely. The attended workshop session was held at Jurys Inn with those online split into a couple of groups and discussing the issues with each other remotely. We all came together again in HQ for the ﬁ nal feedback session. With a lot of hard work and goodwill from everyone involved, it worked.

What do we do in the future? There are some who argue that all future meetings should remain online – they are time-eﬃ cient, more accessible to all and save on travelling. Conversely, there are others who are missing being able to meet up at attended events and wish to see a rapid return to that format. There is also a further group of members who are advocating blended events like the one held last March – but will members physically attend an event if they can watch it online instead? And, as mentioned above, any conference, be it attended (as had been planned for Acoustics 2020 in Chester in May last year) or online as Acoustics 2020 became last October, attracts a cost to set up – a cost the Institute has to recover from the delegate fee. So whatever event is proposed, some certainty has to be secured over the number of delegates that would pay to attend. Trying to come up with a plan is the challenge currently facing members of our Meetings Committee, chaired by Chris Turner. The Executive Committee is working closely with them. In addition, there are some other members who are also kindly helping to identify both the technical opportunities and constraints that we need to take into account when determining our approach to meetings. Most importantly, we must understand what you, the members, want us to do. One of the immediate issues is whether Acoustics 2021 can be held in person in October this year. At the moment, all that can be said is that there WILL be an event, but the format has yet to be decided. So please make sure you have 11th and 12th October 2021 in your diary.

What we have learned from online meetings Now we have the prospect of the restrictions easing, we are having to think very carefully about our future meeting plans. The enforced use of Zoom (other similar online tools are, of course, also available) has helped us to learn a lot. In no particular order they are: • Online meetings enable us to reach members who would otherwise, because of their location, ﬁ nd it really diﬃ cult to attend any IOA meetings, and certainly not the traditional evening Branch meetings; • Online Branch meetings and webinars can be easily held at lunchtime or in the early afternoon (as opposed to the evening) meaning that members with childcare responsibilities can attend; • Live online presentations work and good debates can occur both with the speaker and between delegates through the chat function. Those live presentations also do come with the added frisson of whether the wi-ﬁ will co-operate throughout the event. • We can hold online multi-session conferences, but to be held robustly and eﬀ ectively they do come at a cost; and • Although we can have some form of online networking, it has never been the same as being in a bar or a pub with fellow delegates, even if individuals sorted out their own refreshment.

a 37

In the meantime, stay safe

ACOUSTICS BULLETIN MAY / JUNE 2021 5

INSTITUTE AFFAIRS Engineering Division

The IOA Engineering Division will support you thr o ugh the process to help you become one of almost 225,000 regist ra nts th a t hold international professional recognition.

By Blane Judd BEng FCGI CEng FIET F CIBSE, Engineering Manager

so please bear with us. Neil Ferguson continues to help us with academic equivalence support for those candidates who do not have exemplifying qualiﬁ cations. You can check for yourself if your qualiﬁ cations meet the required speciﬁ cation by visiting the Engineering Council website www. engc.org.uk . But please don’t panic if your speciﬁ c qualiﬁ cation is not listed, as we can still help you through the process on the individual route. Each institute has an Engineering Council liaison oﬃ cer who comes from another institute as a volunteer to help a n d support colleagues. We are d e lighted to have Malcom Carr- W e st from the Institute of A gricultural Engineers as our new oﬃ cer. Some of you may meet him, as on occasions he might sit in on interviews.

The UK Standard for Professional Engineering Competence and Commitment (UK-SPEC)

Fourth edition

Published August 2020

e are still observing the lockdown rules and the majority of our activity is being conducted while working from home. The interviews we held in February went very well and on the facing page you can read about two of the candidates who were successful. Candidates are provided with guidance material when they ﬁ rst apply, and we are always ready to comment on the content of their professional review report prior to them submitting their ﬁ nal draft. Work continues to draw up the new documentation to comply with the new UK-SPEC version four and are looking to start implementation in the middle of the year. If you want to learn more about the

new version, visit the Engineering Council website at https://bit. ly/3cEALQu . Those already working on their submission will be able to use UK-SPEC version three up to the end of the year. From July onwards, however, we will be encouraging candidates to work to version four. The Engineering Council are expecting us to have made the transition by December 2021. Since on average it takes six months to complete the process, July is considered to be a suitable start point for transition.

Above: Work continues to draw up the new documentation to comply with the new UK-SPEC version four

Interviews Our next round o f inte r views will be later in the year and, as usual, we have candidates working towards interview dates. We hold a number of interview events through the year, depending on the number of candidates we have coming forward for registration. If you are interested in taking the next step to becoming a professionally registered engineer, contact us on acousticsengineering@ioa. org.uk sending a copy of your CV and copies of certiﬁ cates and transcripts of your qualiﬁ cations. It is important that we have all of your further and higher education certiﬁ cates, not just your highest attainment.

Help and support Emma Lilliman is doing a great job in managing the process remotely, we are working hard to keep response times down to a minimum while working remotely

6 ACOUSTICS BULLETIN MAY / JUNE 2021

Engineerin: wens ?

Academic qualifications The requirements for academic qualifications for CEng and IEng changed in 1999. Pre-1999 an honours degree at 2:2 or above was required for CEng or a higher diploma/certificate for IEng. Post-1999 this changed and for CEng a master’s degree was required or an ordinary degree for IEng.

Remember that we are here to help you get through the process and advice and support is offered to every candidate personally. For the individual route, the Institute accepts a number of courses in relevant subjects such as audio technology from certain academic centres, as being equivalent to accredited courses for the purposes of EC registration, without the need for further assessment. The Institute recognises the IOA Diploma course and the several masters courses linked to it as providing evidence if you are looking to gain CEng registration. You could also offer a PhD qualification, depending upon the content of the associated taught element. We can also offer support for registration via a ‘technical

report’ route, if you do not have the relevant qualifications to help you demonstrate you are working as a professional engineer in acoustics. The election process is overseen by the Institute’s Engineering Division Committee, which is made up of volunteers from the membership, to whom we are extremely grateful. They represent the 300 or so members holding EC registration. They provide the essential peer review process that affirms that you are at the appropriate level for recognition as an Engineering Council Registered Professional Engineer. The opportunity is there, and we are ready to support you through it, so that you can become one of almost 225,000 registrants that hold International professional recognition.

There are two routes: 1. standard route if you have the appropriate EC-accredited qualification (also referred to as an exemplifying qualification) in acoustics; and the 2. individual route , which requires further preparatory work from you before submitting evidence of your competence.

Candidate profiles

Matthew Robinson BSc, PhD, CEng, MIOA I studied audio technology at Salford University, graduating in 2008, with a year in industry spent at the Building Research Establishment. Following this I applied for research funding for a PhD at the University of Liverpool Acoustic Research Unit. My work focused on the prediction of sound and vibration in buildings from transient and quasi-transient sources using transient statistical energy analysis. After graduating I took on a post-doc research project, working with HMG Communications Centre, developing methods for assessing speech security. In 2013, I moved from academia to commercial consultancy and started working at Sandy Brown in Manchester. In the intervening years I have worked on a wide variety of schemes in the northwest, London and internationally. I first considered starting the registration process a few years ago and the IOA were helpful in confirming that I would need to proceed with the ‘standard route’, as my PhD would serve as an alternative for an accredited engineering degree. In discussions with the IOA, I realised that I needed to gain more experience in commercial consultancy prior to applying. The process of writing the professional review interview (PRI) report was useful in a few ways as I had to review my input for a number of projects and evaluate the design guidance, decisions and technical methods. The process also allowed me to look at how the work that I do relates to the UK Standard for Professional Engineering Competence (UK-Spec) assessment criteria, which was essential preparation for the interview. Though for myself, like many

engineers, writing this much about my own abilities was odd and took a while to get used to. The overall experience of professional registration has been useful, but daunting at times. Nonetheless, I would encourage all those practicing acoustics to consider applying.

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Jon Lee CEng, IOA corporate member After becoming an Incorporated Engineer in 2013 I was advised on the next steps to take towards chartership, one of which was keeping an active and up-to-date CPD record. This was one of the greatest benefits to my application, saving me hours of retrospective record keeping and I would recommend keeping on top of it to ultimately obtain chartership. The application process, despite COVID-related delays, was relatively straightforward and the support of the IOA certainly helped in developing a qualifying submission. The interview was held remotely over Zoom, which considering I live overseas was very helpful. There were some challenging questions raised by the panel, a couple of which I actually followed up with a bit of personal research post-interview to solidify my knowledge further in those areas. I would highly recommend the process to those acousticians wanting to develop their career.

ACOUSTICS BULLETIN MAY / JUNE 2021 7

INSTITUTE AFFAIRS

The IOA Diploma during the pandemic

Thanks to the eﬀ orts of many people, the Diploma has continued to be oﬀ ered throughout the pandemic, by distance learning (DL) and at accredited centres.

By Professor Keith Attenborough, IOA Education Manager

measures. London South Bank arranged for the issue of suﬃ cient equipment to enable their Diploma candidates to carry out laboratory work at home. Feedback from the September 2020 centre-based Diploma cohort has generally been extremely positive, with students appreciative of the eﬀ orts made by academic staﬀ and the technical support teams at centres. Similar provisions are in place for the current centre-based Diploma cohort at Derby, Leeds Beckett and London South Bank. However, in February 2021, Solent decided to close its acoustics teaching. We are grateful to Chris Barlow and Juan Battaner- Moro for acquiring the necessary equipment and arranging facilities to enable transfer of the Solent area Diploma teaching to a consultancy. They have been recently accredited

n the Diploma year from September 2019 to December 2020, there were 56 DL and 51 centre-based candidates. However, the continuing pandemic has restricted the number of candidates registered during the Diploma year that started in September 2020 to 38 DL and 36 centre-based. Accredited centres were able to adapt eﬃ ciently to an online mode of delivery. For example, the University of Derby used Blackboard Collaborate to deliver online lectures and enable group tutorials in breakout rooms. Pre-recorded lectures and mini-bite problem solving sessions were uploaded onto the Blackboard platform and MS Teams was used for individual tutorials to support students. Derby, Solent and Leeds Beckett oﬀ ered live laboratory classes subject to COVID safety

(online) for delivering the Diploma and the Environmental Noise Certiﬁ cate course.

Exams The main changes for distance learning candidates during 2019/20 were time-restricted ‘at home’ examinations and a greater proportion of online tutorials. The more open book nature of the examinations required extra eﬀ orts by the examiners to reduce the proportion of questions that could be answered simply by copying from books. Despite this change in the nature of the examinations, the proportions of passes and merits following moderation in August 2020 were much the same as in previous years. Although some Diploma candidates were able to pursue the Diploma projects they proposed in February 2020, many had to amend their plans, since COVID restrictions in the summer months prevented measurements and/or access to facilities. Accordingly, tutors and the IOA oﬃ ce were lenient in allowing changes even at the last minute and new marking criteria were drafted for projects; based essentially on literature review and desktop activities. Similar provisions are in place for the current cohort.

Below: Diploma candidates during laboratory exercises

Virtual home-based laboratory experiments During the current year, the examinations will be time-restricted ‘at home’ again. But another important change has been the introduction of virtual home- based laboratory experiments for candidates who would otherwise have had face-to-face laboratory schools at Liverpool and Dublin.

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INSTITUTE AFFAIRS

ANC Acoustics Awards 2021

If you are working on interesting projects this year, don’t forget the ANC Acoustic Awards 2021 .

These awards are scheduled for November – and now is the time to start about thinking about entering.

Above: John Kennedy, Diploma tutor at Trinity College Dublin, devised experiments involving home-based measurements of reverberation time and audiometry

You could be a winner, like these from 2020...

The laboratories in Dubai took place as normal. The virtual laboratory schools show videos devised by the tutors at Liverpool and candidates watch the videos during a Zoom meeting for up to three hours for each of the experiments. They make subjective assessments of the eﬀ ects of any noise control measures introduced to complement the objective measurements displayed on the instruments. The videos are shown as a series of short clips followed by group discussion of the implications of what has been shown. Candidates take detailed notes in a laboratory notebook, which they use as the basis for reports that they submit for assessment. In a related development, John Kennedy the Diploma tutor at Trinity College Dublin, devised experiments involving home-based measurements of reverberation time and audiometry. DL candidates are required to write up at least one of these for assessment. Although the home-based and virtual laboratory exercises were developed as a consequence of force majeure during the pandemic and they cannot substitute completely for hands-on and group laboratory experiences, there will be discussions at the upcoming meetings of tutors and examiners and education committee in July of whether a version of the virtual laboratories could be oﬀ ered to DL candidates, for example, those based overseas (apart from the Middle East), in the future. This might help the planned drive to recruit more overseas candidates for the Diploma. Already, there are 13 applications (resulting in ﬁ ve registrations so far) from overseas for the Diploma year starting in September 2021.

www.theanc.co.uk/anc-awards- 2020-results/

The Awards look for projects which demonstrate delivery of value and quality for the client, go beyond current good practice, justify how any problems were overcome, show creativity and innovation.

Size and prestige of the overall project are not significant as these awards recognise the acoustics consultancy within the project.

2021 Categories

• Environmental • Vibration Prediction & Control • Innovation • Building acoustics • Smaller Consultancies

Blended learning videos The online provision for the tutored distance learning version of the Diploma has been much enhanced by the series of blended learning videos produced last year. The videos for the General Principles of Acoustics and the Specialist Modules on Regulation and Assessment of Noise, Environmental Noise and Building Acoustics are an integral part of the tutorial programme already and it is planned that those for the Noise and Vibration Engineering Control Module which are still in production will be available in time for the start of the next Diploma year.

More details will follow on the ANC website: www.theanc.co.uk/anc- awards/

Images The image on the ﬁ rst page of this article was taken before lockdown in March 2020.

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INSTITUTE AFFAIRS

The Space Industries Act 2018 Consultation on draft guidance to the regulator on environmental objectives relating to the exercise of its functions under this Act

The Space Industry Act 2018 (the Act) and regulations made under it are a critical part of the Government’s commercial spaceﬂ ight programme. Spaceﬂ ight has the potential to aﬀ ect climate change, local air quality and environmental and underwater noise impact which can aﬀ ect human health, biodiversity and the wider environment. The IOA responded to the Department for Transport Consultation in March and we publish the response in full here.

he IOA welcomes the approach of setting environmental objectives for the spaceﬂ ight regulator and for providing guidance on those objectives. The IOA response focuses on two aspects of the draft guidance, namely:

1. Noise – pages 15 – 20 of the draft guidance 2. The noise aspect of the marine environment

It can be seen that the Institute has various comments on these issues. The IOA would be happy to liaise with oﬃ cials in order to assist in developing the noise-related guidance over the coming months.

Noise The consultation document asks two questions in relation to noise. They are: Q6 Is it clear from the guidance how the regulator should interpret the government’s objective on noise? and Q7 Do you have any comments on the speciﬁ c guidance provided to the regulator on the objective related to noise? Please provide details. P14

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INSTITUTE AFFAIRS

The Institute’s responses are: Question 6 No Question 7 Yes – please see below Further details It is understood that the guidance is required to address the assessment of noise impacts from a new spaceport and the impact of space ﬂ ights associated with the spaceport. Therefore, when providing guidance, it is convenient to divide the issues into four elements: • Policy, legislation and guidance; • Prediction; • Assessment; • Mitigation.

Through the eﬀ ective management and control of environmental, neighbour and neighbourhood noise within the context of Government policy on sustainable development:

of their operations, little work has been published assessing the community noise impacts from rocket operations. However, before the community noise impact can be assessed and, if necessary, mitigation considered, noise prediction and modelling studies are needed to help better understand the potential noise exposures of the surrounding communities from rocket launches at spaceports. It would be helpful if these studies were required to produce outputs in formats that build on and can be integrated with existing aviation noise data, e.g., airport noise contours. This would particularly be the case if spaceports might be developed at existing airports or airﬁ elds as well as where new sites are proposed. Spacecraft noise has characteristics that make it diﬀ erent in how the sound propagates compared with other noise sources e.g., the distance at which the sound waves’ transitions from relative low rates of decay to more rapid decline can be longer than for other sources. Consequently, many of the established methods for predicting noise propagation are not as accurate as they may be for other sources. Some of the approved spaceports in the USA have followed empirically derived NASA noise prediction methods for evaluating the acoustics, vibration and blast environment when selecting the location of a potential spaceport. However, these methods are dated and do not take into account the new types of spacecraft designs and take oﬀ methods that are to be found. With recent technological advancements, the concept of horizontal launch vehicles is quickly becoming a new category of spacecraft. Although various noise prediction models have been developed and used for spaceports, there is no single uniﬁ ed approved method. Consequently, the IOA suggests that the guidance also requires that the Scoping for any Environmental Statement (or equivalent where the EIA regulations may not apply), for a spaceport should include a comprehensive review of available models and methods for prediction of space travel related noise and a detailed explanation of the reasons for using a preferred chosen method.

• avoid signiﬁ cant adverse impacts on health and quality of life; • mitigate and minimise adverse impacts on health and quality of life; and • where possible, contribute to the improvement of health and quality of life. The National Planning Policy Framework would also apply to the new spaceport. It includes the policy that states:

The Institute’s comments below are set out under those headings.

Planning policies and decisions should contribute to and enhance the natural and local environment by:

Policy, Legislation and guidance Some of the information given in the draft guidance document really has no bearing on the issues to be addressed in the Assessment of Environmental Eﬀ ects (AEE) of such a development. Such information includes: • The reference to the Environmental Noise Directive, and presumably the associated transposing regulations. When considering the development of a new spaceport – this legislation has no bearing; and • The Environmental Protection Act 1990 (EPA1990). This legislation would only potentially apply once the spaceport has been built and should a noise source at the spaceport, which falls under the terms of the EPA1990, be thought to be causing a statutory nuisance. Furthermore, noise from aircraft in ﬂ ight are excluded from the ambit of this legislation and spacecraft could fall under the deﬁ nition of an aircraft.

e) preventing new and existing development from contributing to, being put at unacceptable risk from, or being adversely aﬀ ected by, unacceptable levels of … noise pollution; This policy would also apply, and, therefore, should also be part of the Environmental Objectives. The Planning Practice Guidance on Noise includes a Noise Exposure Hierarchy Table which provides assistance for implementing these policies. That table can be found here: https://assets.publishing. service.gov.uk/government/ uploads/system/uploads/ attachment_data/ﬁ le/820957/ noise_exposure_hierarchy.pdf Using these three documents provide the Environmental Objectives for the Regulator and the associated guidance for meeting them when developing a new spaceport. As noted on page 16 of the draft guidance document, similar approaches to the management of noise can be found in the devolved administrations. Where appropriate, therefore, the guidance needs to be reﬁ ned to reﬂ ect any detailed policy diﬀ erences in Wales, Scotland and Northern Ireland.

The overarching policy for noise management in England is set out in the Noise Policy Statement for England (NPSE), which is mentioned on page 16 of the guidance. In terms of setting environmental objectives for the management of noise on people, the aims of the NPSE should become the Environmental Objectives set by the Secretary of State. These aims apply to all noise sources. Following this approach would not only provide consistent noise management, but are familiar concepts with practitioners. The aims are:

Prediction During the planning phase of any space related development there will be a need to predict noise from the scheme. Despite the increase of rocket launches in the past years and the commercialisation

14 ACOUSTICS BULLETIN MAY / JUNE 2021

Furthermore, the guidance should encourage sensitivity tests using, where available, alternative methods but based on the same inputs as used for the preferred method, so that the uncertainty of the prediction work can be understood. The IOA agree with the draft documents’ advice that relying solely on the L eq,T noise metric time averaged over long periods to predict and assess impacts is not the most appropriate method to use. In addition, indicators including the following are also recommended:

• The maximum noise level in a noise event i.e., launch or recovery of an individual spacecraft e.g., L Amax. • The overall noise energy in a noise event e.g., the SEL (the Single Event Level) and L Aeq,T (the total noise energy over the event period, T). • The degree to which the noise event exceeds the typical prevailing sound levels at receptors. • The frequency content of the noise event and the prominence of any dominant frequencies compared to the prevailing sound. • The onset time of the noise i.e., how quickly the sound level goes from relatively low level to maximum and vice versa. • Assessing the likely eﬀ ects of the above acoustic impact data by contextualising it in terms of factors including the number, duration and timing of noise events per day, week, month and year. CAP 1766 Emerging Aircraft Technologies and their potential noise impacts indicates that the CAA’s Environmental Research and Consultancy Department (ERCD) has been playing a part in the work of the International Civil Aviation Organisation developing noise standards for supersonic aircraft, and the IOA suggest that ERCD could provide noise emission levels for the prediction of noise from spaceports in the UK.

annoyance and sleep disturbance responses to noise without such features, and can have indirect eﬀ ects such as causing resonant vibration in lightweight structures and building elements. Consequently, reliance on the advice and recommendations of standards and guidance that are appropriate for sounds without such content, such as, BS 8233 and the WHO Guidelines, may not be appropriate. Infrasound is noise energy at or below 20 Hz. At normally encountered environmental levels infrasound is not audible to most people. But spacecraft can produce very high levels of sound, including at infrasonic frequencies that may be so high they can become audible relatively near to the source. Whilst the risk of signiﬁ cant adverse eﬀ ects from infrasound is small, it is worthwhile noting that it is a perennial issue which is often misunderstood and/or misused in regard to various forms of development, and that addressing the issue early in the development of policy may help avoid protracted and polarised debate and opposition, which might delay or distract from achieving policy aims.

eﬀ ects of noise, the spaceport guidance should avoid implying the WHO guidelines can be used as set standards to be achieved. Any such standards or thresholds to be used should be set by national or local authorities taking account of the local and national context in order to achieve the relevant policy requirements. The consultation documents also refer to a WHO guideline for L Amax levels to avoid hearing damage. The IOA believe it would be more consistent to refer to the Control of Noise at Work Regulations 2005 which quote a lower exposure action value of a peak sound pressure of 135 dB (C-weighted). As mentioned earlier, the noise from spacecraft can be quite diﬀ erent from other sources. It is usually intermittent but can last for up to several minutes when it happens. It also can occur at extremely high source sound levels, meaning it can propagate over long distances and aﬀ ect a wide area. It often contains a strong low frequency element, including infrasound (see below), which leads to enhanced propagation, triggers diﬀ erent

Assessment The draft guidance mentions the World Health Organization (WHO) guidelines. Whilst the WHO guidelines provide a useful body of knowledge on the likely health

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Space Industry Act 2018 ev ptt i in ferme sore Ecpygusteremereesy ain pte coyote Seo ae aepera stermencagett

INSTITUTE AFFAIRS

The consultation document correctly notes that noise could impact both humans and wildlife, including domesticated animals and livestock. There is little UK speciﬁ c guidance on assessing the eﬀ ect of noise levels on animals, and it may be helpful for the regulator or another body (e.g., CAA or ICCAN) to suggest any internationally available material that might be used. Finally, on page 17 there was an inconsistency in the metrics used. The IOA propose that the wording should say: To avoid and minimise the risk of structural damage, the maximum noise levels (L Zmax ) should never exceed 110 dB. The IOA recommend that the advice should include a

statement that, Where possible the maximum noise level should be mitigated to less than 90 dB L Zmax to minimise the risk of induced resonant vibration in lightweight structures and building elements e.g., windows. It is also recommended that it is made clear that these values relate to a location outside the potentially aﬀ ected properties.

ICAO Balanced Approach should be mentioned, i.e.: • noise at source; • land use planning; • operating procedures; and • operating restrictions.

The consultation document notes that due to impacts on civil aircraft operations and for meteorological reasons, operators may prefer to launch at night. It is very well recognised, however, that the potential impact of noise at night on human health can be great. Given that the draft guidance notes that noise from spaceﬂ ight activities is anticipated to be one of the biggest environmental concerns for both the impacts on human and wildlife receptors, the IOA would suggest that spaceports

Mitigation The hierarchy of noise controls shown in Figure 1 is not recognised as a mitigation hierarchy for environmental noise management. Furthermore, it is arguably not correct in its details. Instead, with regards to when the spacecraft are in the sky or about to take-oﬀ , the IOA suggests that the

Below: Currently, the regulatory basis for protecting the noise environment in the oceans is ill-deﬁ ned. This guidance has the opportunity of taking the lead in beginning to deﬁ ne good practice

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The noise aspect of the marine environment The consultation document asks two questions in relation to noise. They are:

should be located sympathetically with civil aviation ﬂ ight paths so that there is no need to operate at night. There is a strong case for the Regulator to state that there should be no night operations as a speciﬁ c operational restriction for planned spaceport operations.

opportunity of taking the lead in beginning to deﬁ ne good practice. The potential noise impact of developing and running the infrastructure is reasonably well understood, based on other similar developments, but the impact of the space vehicles is novel and will obviously need investigating and mitigation strategies developed. In particular shock waves due to sonic booms and their likely depth penetration must be characterised. Previous measurements on Concorde should provide helpful examples. Before assessing any noise impact, however, the current noise environment in aﬀ ected areas must be established, both due to natural sources and due to anthropogenic noise. Also required would be an assessment of the species present in the area under consideration (including possibly human divers) and their sensitivity to noise disturbance. Finally, the potential for debris falling from space vehicles and impacting marine life on or near the surface, oil rigs, and other oﬀ shore installations would require assessment.

Q6 Is it clear from the guidance how the regulator should interpret the government’s objective on the marine environment? and Q7 Do you have any comments on the speciﬁ c guidance provided to the regulator on the objective related to the marine environment? Please provide details.

Noise – conclusion The IOA are of the view that the aims and objectives of existing noise policy and guidance suitably account for spacecraft related noise. However, standards and guidance commonly used in the UK for other noise sources are only partly suitable for spaceport related noise. Therefore, it is suggested that the Government should commission a study to collate and review evidence on the eﬀ ects of space travel related noise. This could then inform development of suitable guidelines and standards incorporating Government policy aims and objectives which seek to balance the negative eﬀ ects of noise with the positive economic and social beneﬁ ts of development.

The Institute’s responses are: Question 6 No Question 7 Yes – please see below

Further details The draft guidance provided to the regulator on the marine environment is vague. It makes many suggestions for top level strategy, but does not consider actually what should be done or how to do it. Currently, the regulatory basis for protecting the noise environment in the oceans is ill-deﬁ ned. This guidance has the

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By Tom Galikowski, Group Chair IOA Early Careers Group

he Early Careers Group (ECG) has continued to organise events forming a series of webinars prepared in response to COVID-19. The University Fair, held on 8th February received good feedback from both attendees and the speakers. On 8th March, the ECG organised an ‘Ask Anything’ event encouraging members of the IOA to submit questions for which answers are not easily found on the web or by asking colleagues. (IOA members can catch up with the event here https:// www.ioa.org.uk/members-video- links-branch-group-and-other- meetings-2019-20 ). We have received many interesting questions – thank you. Read below for a summary report of the event. All webinars and events are possible due to time and eﬀ ort volunteered by our guests and my fantastic ECG colleagues – Daniela Filipe MIOA from Hoare Lea, Dr Nikhil Mistry MIOA from ISVR and Josie Nixon MIOA from HA Environmental, as well as enormous help (and patience) of Linda Canty and Alex Shaida from the IOA. We are always on the lookout for CPD ideas – please get in touch if there is a technical, career and education-related topic you would like to be discussed. We have welcomed new ECG representatives: Zanyar Abdalrahman (Scottish Branch), Chris Duﬃ ll (Welsh Branch), Jonas Lopez Montoro (London Branch) and George Taylor (Noise and Vibration Engineering Group). There are still vacancies at Central

thought were most pressing in their relevant ﬁ elds: • Dr Amelia Gully recognised the use/misuse of machine learning techniques being applied to speech and hearing problems without understanding of the underlying systems. Interpretable AI setup is needed to use acoustics knowledge to inform the models and learn from them. • Dr James Talbot singled out ground borne vibration as one of the areas to pay attention to. This area of acoustics is inherently diﬃ cult and does need a good understanding to accurately guide the design. There are propagation models available but, as Dr Talbot put it, a bit of knowledge is dangerous. As a result, each element needs to be boiled down to ﬁ rst principles to understand and manage uncertainty of the design. • Daniela Filipe (Hoare Lea, ECG rep in the IOA Building Acoustic Group) identiﬁ ed overheating as the issue requiring attention. Further research is needed on how noise impacts people at home to inform recommendations for normal and overheating conditions. Dr Nikhil Mistry, Stephen Turner and Professor Attenborough, all agreed that the proﬁ le of acoustics needs promoting to the public and private sectors. Awareness that sound and vibration are an inherent element of every aspect of our lives needs raising. Question: What is the maximum hearing range of a human? This was one of the questions that we come across often in our

Branch, Research Committee and Physical Acoustics Group – if you are interested, please get in touch with the ECG or the relevant groups. On 1st April we started a mini- series of webinars building on the popular ‘The Art of Being a Consultant’. Five bi-weekly discussions were organised focusing on topics not usually discussed during the in-person event, such as the role of mistakes, networking, working remotely or designing calculations. A summary of the event will be published in the July-August issue of Acoustics Bulletin.

ECG ‘Ask Anything’ webinar The event aimed to encourage members to ask unusual questions about acoustics. We invited experts in their ﬁ elds to help us answer some of the more interesting ones and take part in a discussion. They were: Professor Keith Attenborough (Open University, IOA Diploma), Dr Amelia Gully (University of York, ECG rep in the IOA Speech and Hearing Group), Dr Nikhil Mistry (ISVR, ECG rep on the IOA STEM Committee) and Dr James Talbot (University of Cambridge). We also received contributions from Professor David J Thompson (ISVR) who emailed his response and Matt Robinson (Sandy Brown) who pre-recorded his answer.

Question: What is the most pressing issue in all of acoustics right now? This open-ended question was interesting as it did not focus on a speciﬁ c discipline. Therefore, we asked our experts, what issues they

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industry. As expected, the answer is not that straightforward, and even the question itself needs clariﬁ cation. Dr Gully pointed out that it requires the sound pressure level to make sense. Human hearing varies at diﬀ erent sound levels. Starting at the bottom of the equal loudness graph, near 0dB, the hearing range is around 1 to 5kHz, broadening with the sound level increasing. Additionally, human hearing varies between individuals. As a general rule of thumb, the hearing range of 20Hz– 20kHz is about right although in reality it is probably slightly smaller.

show 5 that explored what kind of sounds these dinosaurs were likely to have made. Some dinosaurs are related to modern birds and are the same division as crocodilians. Using the infrasound sound made by alligators, the show dropped it by three octaves, resulting in a rumbling and ominous sound. A T-rex could not roar as it did not have a larynx. Dr Mistry referenced the project ‘Rawr’ 6 where a fossilised sull was used to create a physical model allowing scientists to pass air through the skull of another dinosaur and hear the sound.

Question: Is snow a good sound absorber? Many of us notice the diﬀ erence in reduced background noise but is it caused by the snow or by less road and pedestrian traﬃ c? Professor Attenborough provided a detailed answer, referencing a paper he co-authored with Othmar Buser in 1988 1 . Mr Buser was interested in ﬁ nding out if sound can be used in predicting avalanches and as a result did a lot of measurements of snow using an impedance tube. However, since the measurements did not ﬁ t the prediction model, Professor Attenborough was approached to help interpret the results. It became apparent that the speed of sound in air at -5 degrees Celsius and at high altitude of Swiss Alps (resulting in low air pressure) was 328 m/s – much slower than the widely known 340 m/s. Another research from 2015 2

Question: In sound insulation tests, what is the physical diﬀ erence between airborne noise and impact noise? The question was answered by Matt Robinson with additional information from Stephen Turner. In both instances, a speaker and a tapping machine put a solid obstacle into motion, creating sound waves on the other side. The key diﬀ erence is what is being excited. A speaker excites the air around which has the same impedance. A tapping machine on the other hand is mechanically exciting an element which has its own impedance, varying depending on its construction and thus aﬀ ecting how it sounds. Airborne sound excites the whole of the partition whereas impact (like footfalls) excites primarily one area.

Question: When it comes to vibration from railway, why is it that often only an assessment of the VDV is required and not the re-radiated noise? This question was jointly answered by Professor Thompson and Dr Talbot, with additional points raised by Brain Hemsworth. It was agreed that the question is really about policy. It is true that re-radiated levels are audible rather than being felt. The legislation, however, is based on the external airborne noise levels and there are no statutory noise levels for ground borne noise, which depends on the internal conditions and properties of the building. For surface railways, the external noise levels are often up to 90 dB(A) and above, which will dominate the airborne noise within the building. Since there are more surface railways – with exception of London – the policy lends itself to VDV assessment associated with perceptibility of vibration. VDV is coded up and is accepted for all sorts of vibration sources. Re-radiated noise on the other hand, does not lend itself to an easy codiﬁ cation with people being much more sensitive to low frequencies and measurements, prediction and assessment are diﬃ cult as they depend on many more factors including building response and psychology. Although there are useful guidelines including the Federal Transit Administration and the ANC guidelines, there is no international standard.

measured diﬀ erent kinds of snow (e.g., new or dense) from the Himalayas and concluded that snow is indeed a good absorber. A 4cm layer of new snow is better than a 4cm layer of mineral wool or melamine foam. Snow provides a better destructive interference at lower frequencies than grassland and this explains why it is quieter when there is snow about. Professor Attenborough referenced measurements carried out by Parkin and Scholes in 1965 3,4 , demonstrating that a fresh snow cover reduced the ground attenuation frequency from 400-500 Hz to 100 Hz.

Question: Should we introduce impact testing for walls under Building Regulations? Matt Robinson suggested that this was not required. Impact noises on walls come from ﬁ xed items such as lifts or ductwork and to mitigate these sources, this is often considered at design stages. Fixing would be diﬀ erent for diﬀ erent sources and, therefore, any robust testing method would need to include them all. Matt noted that the industry should focus on BS EN 14366 or BS EN 15657 instead as these look at the designs of how impact noise in walls are considered. If you have any other burning questions about acoustics, email them to earlycareers@ioa.org.uk

Question: What would a dinosaur’s roar have sounded like? We are all familiar with roars generated for ﬁ lms or embedded in toys but are they actually correct? Dr Nikhil Mistry researched various sources to ﬁ nd out and presented the results during the talk. There were lots of diﬀ erent dinosaurs producing diﬀ erent sounds. Dr Mistry focused on the most iconic of them all – a T-rex. The sounds made in the Jurassic Park series were created by using lions’ roar, predominantly purely for the cinematic experience. A reference was made to a BBC

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INSTITUTE AFFAIRS

Early careers – vibration isolation In this column, we highlight the wide range of skills, sectors and regions where early career professionals work. George Taylor of Mason UK, who has recently become the ECG rep in the Noise and Vibration Engineering Group, provides background to his career in vibration isolation so far. “I studied mechanical engineering at Oxford Brookes Engineering which, being based in the heartland of UK motorsport, specialised in developing the next Formula 1 engineers and technicians. Most modules were based on thermodynamics, thermo ﬂ uids (CFD), material properties and stress analysis and thus my only exposure to acoustics was limited to a ﬁ nal year dynamics module. This module covered the basic principles of mass-spring systems and the eﬀ ect of damping in an automotive context. It is quite possible these brief studies, along with my mechanical background, opened the door to a career in noise and vibration isolation. “I joined Mason UK in 2016 and spent most of my ﬁ rst year gaining experience on site projects for installations such as ﬂ oating ﬂ oors which allowed me to gain invaluable knowledge of site logistics. Projects such as the Royal Opera House and the English National Ballet School are a couple of standout examples. I believe this is a really important part of any engineer’s growth in their industry and has certainly added another string to my bow when it comes to acoustic design. I quickly realised how much I enjoyed the problem solving aspect of acoustics and the responsibility of ﬁ nding suitable solutions both architecturally and structurally. Being involved throughout the project from ﬁ rst contact to ﬁ nal delivery makes it all the more satisfying. “IOA conferences, CPDs and social networking have helped me learn more from the wider acoustics industry and is something I am keen to continue in the coming months and years.”

Right: George Taylor

The ECG is open to all members of the IOA (both corporate and non-corporate) who shall normally be under 35 years of age or within ﬁ rst ﬁ ve years of their career. The group is always keen to hear from members and non-members alike. To join the Early Careers Group, to ﬁnd out more information or to voice your concerns, visit https://www.ioa.org.uk/early-careers-group

References 1 Attenborough, K., Buser, O., “On the Application of rigid Porous Models to Impedance Data for Snow”, J Sound Vib, 142 (2), pp 315-327, 1988 2 Datt, P., “Experimental measurements of acoustical properties of snow and inverse characterization of its geometrical parameters”, Applied Acoustics, 101, pp 15-23, 2015 3 Parkin, P. H., Scholes, W. E., ”The horizontal propagation of sound from a jet engine close to the ground at Radlett”, J Sound Vib., 1, pp 1-13, 1965 4 Parkin, P. H., Scholes, W. E., ”The horizontal propagation of sound from a jet engine close to the ground at Hatﬁ eld”, J Sound Vib., 2, pp 353-374, 1965 5 “The Real T Rex with Chris Peckham” (2018) [online], directed by: Mark Everest, UK and Martin Williams, Canada, Talesmith, BBC, Available on BBC Programming Site. 6 Brown, C. et al, “Rawr! Study in Sonic Skulls: Embodied Natural history”, Proceedings of the International Conference on New Interfaces for Musical Expression, Baton Rouge, LA, USA, May 31-June 3, 2015, Online: https://www.nime.org/proceedings/2015/nime2015_325.pdf

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INSTITUTE AFFAIRS

Do ﬁ sh make sound, and, is acoustics really important? Watch an example answer at the IOA YouTube channel

IOA STEM activity – promoting acoustics

Questions asked at the recent IOA Early Careers Group (ECG) online webinar (reported on pages 18, 19 and 20) included: Do ﬁ sh make sound, and, is acoustics really important? I

By IOA STEM Ambassador, Dr Nikhil Mistry

OA members were invited to simply ask anything about acoustics and the ECG committee then sourced answers from other members, who are experts in the ﬁ eld of acoustics related to the question. The aim of this event was to encourage members to speak up about misconceptions and shortfalls in acoustics knowledge, while also exploring some of the more unusual acoustic phenomena in the built and natural environment. An example of an answer can be found at the IOA YouTube channel https://www.youtube.com/watch?v=RVl6iJg0E-4 In opening the ﬂ oor to questions, members can learn a little more about the work other people do in the industry; highlighting the breadth and depth of applications of acoustics.

those who have the ‘coolest’ job amongst other engineers, so let’s try to show the rest of the world that! Please email ideas and comments to STEM@ioa.org.uk

Raising the proﬁ le of acoustics Although this was an IOA event, there is great potential for this to be run at a public level, inviting people of all backgrounds to ask questions about the role and presence of sound and vibration in our lives, helping to raise the proﬁ le of acoustics in the public’s mind. At schools, the syllabus on the science of sound (pardon the overload of alliteration) is quite limited and children are rarely introduced to the idea of a career in acoustics. However, there is the danger that if we allow anyone and everyone to enter questions, we open ourselves to some controversy where political agendas could play a role in acoustics-related projects, which have the population divided in opinion. Nevertheless, there is a lot to be gained by listening to our audience and we can ﬁ nd an eﬀ ective way to ﬁ lter out the troublesome requests. So how do we engage our audience of non-members? What can we give back to them and what can we do to raise your proﬁ le and work in acoustics? The IOA STEM committee plans to attend events, show oﬀ ‘cool’ acoustics and provide educational marketing for the IOA, but I feel we have an obligation to promote acoustics as a sound career choice (apologies, I couldn’t help myself). Acousticians are known as

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ACOUSTICS BULLETIN MAY / JUNE 2021 21

FEATURE

COVER STORY

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Taken on 5 March 2021, this colour-calibrated image from a Navigation Camera aboard NASA’s Mars 2020 Perseverance rover shows tracks from the rover’s ﬁ rst drive (darker marks in the foreground) and an area scoured by the Mars 2020 mission’s descent stage rockets (lighter-coloured area in the middle ground). Image courtesy of NASA/JPL-Caltech

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By Timothy Leighton, ISVR, University of Southampton

On 23 February 2021, news organisations ran headlines such as ‘NASA’s Mars Perseverance rover beams back ﬁ rst sounds ever recorded on another planet’. 1

e know in detail what many of the landscapes on planets in our solar system look like, but decent quality data on how they sound is rare. This not only means that movies generate unrealistic soundscapes for, say, Mars, but we miss the opportunity to infer what is happening in an alien world using complementary signals. Acoustic signals can travel around line- of-sight obstacles that block, for example, the view of a camera.

They can travel through liquids and solids that are optically opaque. The bandwidth and power requirements, and weight and fragility of acoustic sensors can often be less than those of video cameras. The previously slow progress in capturing an alien soundscape 2 took a very signiﬁ cant step forward with the successful deployment of NASA’s Mars Perseverance. Most recordings claiming to be of ‘sound from space’ have not been – often they are the electromagnetic (EM) interference on probe

instruments caused by lightning or charged particles, played back through a loudspeaker (often with some form of time stretching or condensing to get the signals in the audio spectrum, or condense a sequence of rare events into the attention span of the listener). Those signals were never acoustic in the ﬁ rst place. Popular examples include the EM eﬀ ects on Cassini’s sensors of Saturn’s lightning 3 or its bow wave 4 , or the EM eﬀ ect of pulsar emissions on Earth- based sensors. 5 P24

22 ACOUSTICS BULLETIN MAY / JUNE 2021

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Enhance your career prospects in acoustics

The IOA runs a range of certificated short courses nationwide, assessing competence in the areas shown. The courses run twice a year at accredited training centres across the UK (courses are held prior to exam dates and usually run for around five days).

To find out what’s right for you and where in the UK the courses are running, contact the IOA at:

Silbury Court, 406 Silbury Boulevard Milton Keynes MK9 2AF UK Telephone: +44 (0) 300 999 9675 education@ioa.org.uk www.ioa.org.uk

Try ODEON 16 www.odeon.dk

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ACOUSTICS BULLETIN MAY / JUNE 2021 23

FEATURE

Above: This image shows two possible routes (blue and purple) to the fan-shaped deposit of sediments known as a delta for NASA’s Perseverance rover, which landed at the spot marked with a white dot in Mars’ Jezero Crater. The yellow line marks a notional traverse exploring the delta. The base image is from the High Resolution Imaging Experiment (HiRISE) camera aboard NASA’s Mars Reconnaissance Orbiter (MRO). Image courtesy of NASA/JPL- Caltech/University of Arizona

History of extra-terrestrial sound recording Tentative interest in recording genuine acoustic waves from other planetary bodies dates from the 1960s, although it was never a priority of missions and, as such, had limited success, with the exception of Apollo’s lunar seismic data. From 1978 onwards, the ﬁ nal Venera landers on Venus were equipped with microphones, looking for evidence of thunder, but they were only able to measure pressure

ﬂ uctuations on the microphone itself generated aerodynamically by air ﬂ owing past the lander. 6, 7

To be speciﬁ c, these are pressure ﬂ uctuations generated by turbulent ﬂ ow passing over the microphones and are therefore generated locally rather than from some distant source. A single microphone cannot distinguish them from sound, which is why windshields are often used on outdoor microphones. Similarly, although time-series ‘sounds’ were published from the descent

24 ACOUSTICS BULLETIN MAY / JUNE 2021

FEATURE

soundscape, and the medium is not atmospheric, which also is a key component of public engagement in the topic of extra-terrestrial sound. As will be explored later, some of the success of these Apollo missions may relate to the closeness of the Moon to Earth (a radio signal takes around 5s to complete a two-way trip). Of course, if the sensors are on Earth itself, or in near-Earth orbit, the problem of signal delay is removed. An example of this is when acousticians successfully helped to interpret the waves resulting from the collision of Comet Shoemaker- Levy 9 with Jupiter 12, 13 in 1994. Such an opportunistic use of events still represents a major possibility for acoustic missions, whether the sensors are on Earth or in near-Earth orbit (removing the signal delay), or whether they are on a planetary probe (in orbit, atmosphere, ground or liquid) because natural phenomena replace the need for the probe to expend power generating a signal. 14

In a much smaller-scale experiment in 1972, Apollo 17 detected ﬁ ne lunar dust slowly migrating at sunrise through the impact of the dust on three plate microphones, orientated to face diﬀ erent directions. 15-17 The 2014 Rosetta mission 18 to the Comet 67 P/Churyumov-Gerasimenko redeveloped the successful Apollo lunar method 19 of counting, and inferring the velocities of, impacting particles.

(on 14 January 2006) of the Huygens probe through the atmosphere of Saturn’s moon, Titan, these were also aerodynamic pressure ﬂ uctuations on the microphone as the probe descended through Titan’s thick atmosphere. It is also possible that these time series data were artiﬁ cially constructed on Earth from purely spectral information transmitted by the probe, because bandwidth limitations are always important in such transmissions (the author would happily welcome clariﬁ cation on this). 8, 9

active acoustic signals generated by the probe itself, to measure the sound speed in the atmosphere, and the distance to the ground by reﬂ ecting sound oﬀ it. 10

Above: This image shows a large sand dune with bright patches. Martian dunes near the poles often have bright patches in the spring, when seasonal frost is lingering. Image courtesy of NASA/ JPL-Caltech/ University of Arizona

A role for acousticians There is no doubt that there is a role for expert acousticians in the design of instrumentation and missions for planetary probes. The sensors must be designed for extreme environments (the Groza-2 electromagnetic microphone on Venera 13 and 14 was still operational at the 800 K temperatures and 100 bar pressures of the Venus landing site). Public and policymaker engagement 20, 21 is vital to ensure there is the political will to fund acoustic packages on missions, and the understanding of the need to include expert acousticians in the planning and analysis. Acousticians themselves must understand that elements they take for granted, from our experience of using instruments on Earth, often leave us ill-equipped to cope with how diﬀ erently acoustic sources and sensors, and their

The ﬁ rst (and, in my opinion, most successful to date) use of acoustic sensors pre-date even the Venera microphones. Passive seismic sensors detected seismic waves, that were then used to infer the Moon’s internal structure, in the Apollo 11 (1969), 12 (1969), 14 (1971), 15 (1971) and 16 (1972) missions. The data show tidally-induced moonquakes originating at depths equal to about half the Moon’s radius. 11 The example of the successful detection of seismic waves in the Moon (where absence of atmosphere prevents the propagation of sound through an atmosphere, but not through solids such as transducers or moon rocks) represents the ﬁ rst recording of acoustic waves generated by, and directly measured on, another world. However, the frequency is lower than what most people would imagine would represent their ‘hearing’ a

The Venera and Huygens microphone signals are not acoustic; they do not propagate to the microphone at the relevant acoustic wave speed from a source that is distant from the microphone. Furthermore, they do not represent the natural soundscape of the planet. Therefore, neither class as recording the sound of another world, although the Venera data was undoubtedly a pioneering achievement, and the Huygens mission was a triumph in using

Left: This image was taken by the rover’s Navigation Cameras during the ﬁ rst drive of NASA’s Perseverance rover on Mars on 4 March 2021. Image courtesy of NASA/ JPL-Caltech P26

ACOUSTICS BULLETIN MAY / JUNE 2021 25

FEATURE

sounds (e.g., lightning is a known phenomenon on Venus, and – even though Mars lacks liquid-bearing clouds – lightning is a possibility in the larger Martian dust devils) 21 , the sounds most commonly detected by the microphone of Perseverance are likely to be from very close sources. Vehicle noise is exciting (especially if it can be conﬁ rmed to travel through the atmosphere), but the sound of a natural rockfall, would be much more so. However, the acoustic absorption by the atmospheric CO 2 makes the natural soundscape so quiet that future probes and astronauts to Mars may be designed with additional ears on their ‘feet’ to pick up ground-borne sounds when they are not themselves moving. 14 If Mars and Venus have quiet acoustic soundscapes (note I am not including aerodynamic noise on microphones due to relative motion between probe and atmosphere), the next closest thick atmospheres would be on Jupiter and Saturn. However, both Jupiter and Saturn have strong winds and are gravity wells down to crushing pressures, without ground. Hence, on both it would be impossible to land probes in a still atmosphere, and even buoyant missions deploying microphones to capture true acoustic signals above aerodynamic noise levels would be diﬃ cult. Titan represents our only other opportunity to measure the ground-level soundscape in a substantial atmosphere, and indeed Titans’ cold, thick atmosphere carries sound even better that does Earth’s (Figure 1). However, as discussed earlier in the context of the Apollo missions, the proximity to Earth matters in such missions. Radio signals to control the probe take, even at closest approach, a little over two minutes to reach Venus and three to ﬁ ve minutes to reach Mars, so that making an adjustment to correct a mission is feasible before the situation becomes irretrievable (i.e., round trip travel times of under 10 minutes, assuming humans make decisions immediately on receiving the alert). The two-way travel times between Titan and Earth, at closest approach, are two to three hours. The increasing role of on-board artiﬁ cial intelligence should be very useful in mitigating the limitations of that delay. Furthermore, since both Mars and Venus can be reached in under a year, the probe has technology that is only as dated P28

testiﬁ es to the skill, teamwork and dedication of those responsible: it is diﬃ cult to overemphasise the bandwidth limitations that planetary probe missions must work under. The ‘wind noise’ recorded as Perseverance’s microphone descended through Mars’s atmosphere does not represent the sound of another world, since (like the signals recorded by Venera and Huygens ) it represents the aerodynamic pressure ﬂ uctuations on the microphone, rather than soundscape signals that travel over distances at the local speed of sound. We may need a future probe, with a microphone array and a robust sterilised windshield, to distinguish acoustic signals propagating through the atmosphere from other microphone outputs.

EARTH 50

Transmission loss (dB)

0 0.5 1 1.5 2 2.5

Frequency (Hz) x 10 4

TITAN 50

Transmission loss (dB)

0 0.5 1 1.5 2 2.5

Frequency (Hz) x 10 4

VENUS 400

Recordings from Perseverance After its spectacularly successful landing, Perseverance has transmitted further microphone recordings, now notably made from a stationary platform. Those published to date record the sound of the device itself and a ‘wind gust’ on the surface. This is exciting; doubly so if the sound of the device travels through the atmosphere rather than through a solid path in the device (no details are available as yet). Aerodynamic pressure perturbations on a microphone do, on Earth, mimic what might be heard by wind on the ear, and whilst these may convect, they do not represent a soundscape in the way that the sound of, say, a distant rockfall, would. We have to wait for more data to see what of that soundscape might be measured. Barring intermittent nearby dust devils, the natural soundscape of the planet might be very quiet. Our calculations suggest that the high proportion of carbon dioxide in the thin atmosphere of Mars absorbs sound strongly at audio frequencies (Figure 1). 20 Although the densities of Martian and Venusian atmospheres are very diﬀ erent at ground level (0.02 kg m -3 and 65 kg m -3 , respectively – yes, Venus’ ground- level atmosphere has 6.5% the density of Earth’s water!), our calculations suggest that, ironically, our two closest planets are both cursed with being quiet places because of the high proportion of carbon dioxide in their atmospheres (Figure 1). Whilst this does not rule out the detection of intermittent

Transmission loss (dB)

300

200

100

00 0.5 1 1.5 2 2.5

Frequency (Hz) x 10 4

MARS 1200

1000

Transmission loss (dB)

800

600

400

200

00 0.5 1 1.5 2 2.5

Frequency (Hz) x 10 4

Above: Figure 1. The transmission loss as a function of frequency, for various propagation distances. It contains contributions to sound attenuation from geometrical spreading losses and atmospheric absorption. The reference distance in the transmission calculation is 1 m from the source. The colours (line types) indicate the diﬀ erent source – receiver distances: blue (solid) = 10 m; red (dash) = 20 m; green (dot-dash) = 50 m; black (dot) = 100 m. (Reproduced from Leighton and Petculescu [20])

housings, behave on other worlds. Such issues include our assumptions about calibrations and references 22 , end-eﬀ ects and added mass 23 , coupled waves 24 , the engineering formulations for concepts as simple as hydrostatic pressure 25 , and the extraordinary constraints that bandwidth limitations have placed on the ability to transmit even a simple time-series of data. In transmitting a true video, instead of having scientists on Earth reconstruct a video from a sequence of stills, NASA’s Perseverance Mars mission is a pioneer. The spectacular nature and clarity of that video

26 ACOUSTICS BULLETIN MAY / JUNE 2021

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FEATURE

Acoustics may also play a role in the passive exploration of planetary interiors through a range of long-wavelength seismic 11 and atmospheric 13 waves, and in liquids to measure the sound speed, temperature and depths of the vast water oceans that exist on Europa 25

as the delay between the design freeze and the launch. However, the journey to Titan took Cassini seven years, making its equipment and systems considerably more dated when the probe reached Titan’s surface. Consequently, for missions to the gas giants, Earth systems are often communicating with technology that dates from the previous decade.

workers on terrestrial technology to understand what has been overcome. In 1999, a substantially ‘oﬀ -the-shelf’ microphone 30 was ﬂ own onboard the ill-fated Mars Polar Lander , which crashed during descent. The Mars Descent Imager system of the 2008 Phoenix lander had a microphone, designed to record descent sounds as well as any post-landing acoustic events. However, the plans to turn the microphone on were scrapped in order to avoid a technical problem that might have been potentially dangerous to the mission. 2 A testament to the grit, skill and hard work of many people, in spheres from technical to mission planning to support to outreach, the name Perseverance was indeed well chosen.

and other icy moons 14 (and the small lakes of ethane and methane on Titan 28 ). Until we reach these louder worlds, we can marvel that the recent Perseverance brings us a new opportunity: a functioning microphone on a vehicle that, at times, will reside in a still atmosphere. Most recently, the sound of a laser impacting rock, around 3.1 m distant from the probe, is to be used to analyse hardness and weathering 29 . It is diﬃ cult for

Further exploration Whilst we wait for these other soundscapes to be recorded, acoustics has many roles to play. These range from the use of active acoustics in atmospheres for atmospheric active sonar 10 , for windspeed measurements 26 and to infer the physical and chemical properties of those atmospheres 24,27 .

References 1 S. Lewis, ‘NASA’s Mars Perseverance rover beams back ﬁ rst sounds ever recorded on another planet,’ CBS News (23 February 2021) (2021) https://www.cbsnews.com/ news/nasa-mars-perseverance-rover-ﬁ rst-sounds-ever-recorded-another-planet/ (last accessed 28 February 2021). 2 T.G. Leighton and A. Petculescu, ‘Acoustic and related waves in extraterrestrial environments,’ J. Acoust. Soc. Am., 140(2), 1397-1399 (2016) ( doi: 10.1121/1.4961539 ) 3 J.-R. Cook, ‘Lightning Strikes at Saturn,’ NASA (6 July 2011) https://www.nasa.gov/mission_pages/cassini/whycassini/pia14310.html (2011) (last accessed 28 February 2021). 4 Space Audio, ‘Cassini encounters Saturn’s bow shock,’ The University of Iowa. http://www-pw.physics.uiowa.edu/space-audio/cassini/bow-shock/ (2004) http://www-pw.physics.uiowa.edu/space-audio/cassini/bow-shock/t2004_179_oneshock.wav (2004) (last accessed 28 February 2021). 5 Jodrell Bank Centre for Astrophysics, ‘The sounds of pulsars,’ The University of Manchester, http://www.jb.man.ac.uk/pulsar/Education/Sounds/ (2014) (last accessed 28 February 2021). 6 L.V. Ksanfomaliti, ‘Lightning in the cloud layer at Venus,’ Kosm. Issled. 17, 747–762 (1979). 7 L.V. Ksanfomality, F. L. Scarf, and W. W. L. Taylor, in Venus, edited by D. M. Hunten, L. Colin, T. M. Donahue, and V. I. Moroz (University of Arizona Press, Tucson, AZ), pp.565–603 (1983). 8 R. Lorenz (2008) Acoustic Measurements on the Huygens Probe and Other Platforms: A Review (gatech.edu) https://smartech.gatech.edu/handle/1853/26382 (last accessed 28 February 2021). 9 L. Siles (2005)Scientists Release Audio Huygens Sent During Titan Descent. University of Arizona News https://news.arizona.edu/story/scientists-release-audio-huygens sent-during-titan-descent ) (last accessed 28 February 2021). 10 J.C. Zarnecki, M. R. Leese, B. Hathi, A. J. Ball, A. Hagermann, M. C. Towner, R. D. Lorenz, J. A. M. McDonnell, S. F. Green, M. R. Patel, T. J. Ringrose, P. D. Rosenberg, K. R. Atkinson, M. D. Paton, M. Banaszkiewicz, B. C. Clark, F. Ferri, M. Fulchignoni, N. A. L. Ghafoor, G. Kargl, H. Svedhem, J. Delderﬁ eld, M. Grande, D. J. Parker, P. G. Challenor, and J. E. Geake, ‘A soft solid surface on Titan as revealed by the Huygens Surface Science Package,’ Nature 438, 792–795 (2005). 11 Y. Nakamura, ‘New identiﬁ cation of deep moonquakes in the Apollo lunar seismic data,’ Physics of the Earth and Planetary Interiors, 139(3-4), 197-205 (2003). 12 K. Zahnle and M.-M. M. Low, ‘The collision of Jupiter and Comet Shoemaker-Levy 9,’ Icarus 108(1), 1–17 (1994). 13 M.D. Collins, W. A. Kuperman, B. E. McDonald, and W. L. Siegmann, ‘Parabolic equation modeling of azimuthally advected gravity waves,’ Wave Motion 31(2), 131–138 (2000). 14 T.G. Leighton, P. R. White and D.C. Finfer, ’The opportunities and challenges in the use of extra-terrestrial acoustics in the exploration of the oceans of icy planetary bodies,’ Earth Moon and Planets, 109 (1-4), 91-116 (2012) (doi: 10.1007/s11038-012-9399-6). 15 H. Lindsay, ‘ALSEP Apollo Lunar Surface Experiments Package 19 November 1969–30 September 1977,’ http://www.hq.nasa.gov/alsj/HamishALSEP.html (last accessed 28 February 2021). 16 H. Lindsay, ‘ALSEP Apollo Lunar Surface Experiments Package 20 November 1969–30 September 1977,’ http://www.honeysucklecreek.net/msfn_missions/ALSEP hl_alsep.html (last accessed 28 February 2021). 17 Lunar and Planetary Institute (web page), ‘Apollo 17 Mission: Science experiments—Lunar ejecta and meteorite’ (2016) http://www.lpi.usra.edu/lunar/missions/apollo apollo_17/experiments/lem (last accessed 28 February 2021). 18 A. Rotundi, H. Sierks, V. Della Corte, M. Fulle, P. J. Gutierrez, L. Lara, C. Barbieri, P. L. Lamy, R. Rodrigo, D. Koschny, H. Rickman, H. U. Keller, J. L. L_opez-Moreno, M. Accolla, J. Agarwal, M. F. A’Hearn, N. Altobelli, F. Angrilli, M. A. Barucci, J.-L. Bertaux, I. Bertini, D. Bodewits, E. Bussoletti, L. Colangeli, M. Cosi, G. Cremonese, J.-F. Crifo, V. Da Deppo, B. Davidsson, S. Debei, M. De Cecco, F. Esposito, M. Ferrari, S. Fornasier, F. Giovane, B. Gustafson, S. F. Green, O. Groussin, E. Gr€un, C. G€uttler, M. L. Herranz, S. F. Hviid, W. Ip, S. Ivanovski, J. M. Jer_onimo, L. Jorda, J. Knollenberg, R. Kramm, E. K€uhrt, M. K€uppers, M. Lazzarin, M. R. Leese, A. C. L_opez-Jim_enez, F. Lucarelli, S. C. Lowry, F. Marzari, E. Mazzotta Epifani, J. A. M. McDonnell, V. Mennella, H. Michalik, A. Molina, R. Morales, F. Moreno, S. Mottola, G. Naletto, N. Oklay, J. L. Ortiz, E. Palomba, P. Palumbo, J.-M. Perrin, J. Rodr_ıguez, L. Sabau, C. Snodgrass, R. Sordini, N. Thomas, C. Tubiana, J.-B. Vincent, P. Weissman, K.-P. Wenzel, V. Zakharov, and J. C. Zarnecki, ‘Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun,’ Science 23(347), aaa3905 (2015). 19 O.E. Berg, F. F. Richardson, and H. Burton, ‘Lunar ejecta and meteorites experiment,’ in Apollo 17 Preliminary Science Report, NASA, SP-330, Washington, DC, pp. 16-1, 16-9 (1973). 20 T.G. Leighton and A. Petculescu, ‘The sound of music and voices in space,’ Acoust. Today 5(3), 17–29 (2009). 21 T.G. Leighton, N. Banda, B. Berges, P. F. Joseph, and P. R. White, ‘Extraterrestrial sound for planetaria: A pedagogical study,’ J. Acoust. Soc. Am. 140, 1469–1480 (2016). 22 M. A. Ainslie and T. G. Leighton, ‘Sonar equations for planetary exploration,’ J. Acoust. Soc. Am. 140, 1400–1419 (2016). 23 T.G. Leighton, ’Fluid loading eﬀ ects for acoustical sensors in the atmospheres of Mars, Venus, Titan and Jupiter,’ Journal of the Acoustical Society of America, 125(5), EL214-EL219 (2009) (JASA Express Letters) (doi: 10.1121/1.3104628). 24 J.Jiang, K. Baik and T. G. Leighton, ‘Acoustic attenuation, phase and group velocities in liquid-ﬁ lled pipes II: Simulation for spallation neutron sources and planetary exploration,’ Journal of the Acoustical Society of America, 130(2), 695-706 (2011) (doi: 10.1121/1.3598463). 25 T.G. Leighton, D. C. Finfer and P. R. White, ’The problems with acoustics on a small planet,’ Icarus, 193(2), 649-652 (2008) (doi: 10.1016/j.icarus.2007.10.008). 26 D. Banﬁ eld, D. W. Schindel, S. Tarr, and R. W. Dissly, ‘A Martian acoustic anemometer,’ J. Acoust. Soc. Am. 140, 1420–1428 (2016). 27 R.A. Hanel, ‘Exploration of the atmosphere of Venus by a simple capsule,’ NASA Technical Note TN D-1909 (1964). 28 R.D. Lorenz and J. Mitton. Titan Unveiled: Saturn’s Mysterious Moon Explored. Princeton University Press (2010) ISBN 978-0691146331. 29 NASA/JPL-Caltech/LANL/CNES/CNRS/ISAE-Supaero, ‘First Acoustic Recording of Laser Shots on Mars’ (2 March 2021) https://soundcloud.com/nasa/perseverance-mars- supercam-laser-impacts-on-rock-target 30 G.T. Delory, J. Luhmann, L. Friedman, and B. Betts, ‘Development of the ﬁ rst audio microphone for use on the surface of Mars,’ J. Acoust. Soc. Am. 121, 3116 (2007).

28 ACOUSTICS BULLETIN MAY / JUNE 2021

 

OBITUARY

It is with great sadness that we announce the recent passing of our dear friend and former colleague, Dr Trevor Hickman. He was 71. Dr Trevor Hickman

By Dave Clarke, Director at SRL Technical Services Limited

After gaining a physics degree and then a PhD in sound and vibration at Chelsea College Trevor ﬁ rst worked at WS Atkins then Wimpey Laboratories before joining SRL in 1983. He stayed there for over 30 years until he retired in 2014. He worked on many high-proﬁ le projects including the Channel Tunnel and the Millennium Dome (now the O2 Arena). In the 1990s he encouraged many multiplex cinema developers to use a lightweight wall between auditoria. This will have led to a signiﬁ cant saving of the world’s resources in terms of blockwork and aggregates generally which, in turn, made cinema construction just a little more sustainable at a time before ‘sustainable’ was even a word. His expertise in vibration also set him apart from your average acoustic consultant, who normally runs a mile when anyone mentions the word.

A brilliant mind He was instrumental in maintaining the high quality of our work here at SRL, through coaching and mentoring, sharing his knowledge with all staﬀ members, no matter how experienced they were. You never had to worry with Trevor around, as he always seemed to know the answer to even the most obscure technical question. He was our comfort blanket. He had a brilliant mind and also one of the weirdest senses of humour you are ever likely to come across. It is said that he took more pleasure in having to explain the joke to you afterwards – when you couldn’t understand it – than he did telling the joke in the ﬁ rst place. Away from work, he loved playing table tennis (in fact it was at a table tennis club where he met Sue, whom he went on to marry and spend the rest of his life with). He also had a great passion for gardening and enjoyed music (yes, he went to gigs), photography and spending time with his family, especially his grandchildren. We were so very lucky to have known him. Our thoughts remain with Sue and her family.

30 ACOUSTICS BULLETIN MAY / JUNE 2021

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FEATURE

ISO TS 19488:2021 Acoustic classiﬁ cation of dwellings – Coming to a construction site near you!

It is notoriously diﬃ cult to predict exact publication dates for new international standards and guidance documents and, as such, this article is an early insight. However, the expectation is that this will be published about the time you receive this edition of Acoustics Bulletin.

By Philip Dunbavin and Sean Smith

During the four years oﬃ cial lifetime of COST TU0901, close research cooperation and discussions took place involving more than 90 experts from 29 European countries and three non-European countries (Canada, Australia and New Zealand). Most European countries have regulatory sound insulation requirements for dwellings, and speciﬁ c sound insulation classiﬁ cation schemes exist in several countries. However, sound insulation descriptors, requirements and class criteria presented a high degree of diversity and, unfortunately, there was no sign of increasing harmonisation, rather the contrary. This diversity has caused confusion for the building industry and was an obstacle for trade, development and exchange of experience and construction data. COST Action TU0901 was established to initiate changes to this situation to the beneﬁ t of people in their everyday life and for the building industry. It is believed that although regulations are a national issue within each country, if all European countries used the same descriptors and had a joint acoustic classiﬁ cation scheme for dwellings, each country could select a class for regulations, and all sectors involved would, in the long run, beneﬁ t from the harmonisation. Drawing a consensus from such diverse range of experiences and views was not an easy task.

The ﬁ nal reports of this work can be downloaded at https://tinyurl.com/fvmvncxa It was originally intended that this document would be published in 2018 and was sent out as a Final Draft International Standard (FDIS) for international voting. (Please refer to the article on page 64 of the Acoustics Bulletin, January/ February 2019). Unexpectedly, the international voting disapproved this draft standard, due to some unusual tactical voting by a few countries. It was subsequently agreed by the plenary meeting of ISO/ TC43/ SC2 in Japan in November 2018 to reissue this as a draft technical speciﬁ cation. Technical speciﬁ cations are prepared where there is no consensus, or when there is an emerging science, such as soundscapes. A technical speciﬁ cation can eventually be converted into a full ISO at a later date when more evidence is available or a consensus can be reached.

Aalborg Universitet

COST Action TU0901 – Building acoustics throughout Europe. Volume 1: Towards a common framework in building acoustics throughout Europe

Rasmussen, Birgit; Machimbarrena, Maria

Publication date: 2014

Document Version Publisher's PDF, also known as Version of record

Link to publication from Aalborg University

Citation for published version (APA): Rasmussen, B., & Machimbarrena, M. (Eds.) (2014). COST Action TU0901 – Building acoustics throughout Europe. Volume 1: Towards a common framework in building acoustics throughout Europe . DiScript Preimpresion, S. L. http://www.costtu0901.eu/tu0901-e-books

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Scope of ISO 19488:2018 This standard describes class criteria and procedures for acoustic classiﬁ cation of dwellings. The main purpose of this classiﬁ cation standard is to make it easier for developers to specify a standardised level of acoustic quality other than the quality deﬁ ned by national regulations, and for users to require or be informed about the acoustic quality.

his new technical speciﬁ cation, which was published 26 April 2021, had its origin in the European Action COST Action TU0901, (Cooperation on Science and Technology) ‘Integrating and Harmonizing Sound Insulation Aspects in Sustainable Urban Housing Constructions’, which ran from 2009 to 2013.

32 ACOUSTICS BULLETIN MAY / JUNE 2021

This standard can also be applied as a general tool to characterise the quality of the existing housing stock and includes provisions for classifying the acoustic quality before and after renovations have taken place. An additional purpose of this standard is to help national authorities to deﬁ ne a speciﬁ c class in building regulations as the minimum requirement for acoustic conditions in dwellings. For the purpose of this standard, the term ‘dwelling’ refers to detached and attached dwelling-houses, ﬂ ats (apartments) as well as rooms in other buildings used for residential purposes. Energy performance ratings of buildings currently use A to G classiﬁ cations. For the purposes of acoustics and sound insulation, the technical speciﬁ cation classiﬁ cations use A to F.

dwellings. Class A is the highest class, class F is the lowest class. The indication ‘npd’ can be used for dwellings where no acoustic performance is required or determined, or if the performance does not meet the requirements of class F. The classiﬁ cation includes criteria for the six classes A to F for each of the following ﬁ ve acoustic aspects:

area to the walkable surface in common access areas or stairwells and corridors with dwellings opening onto them.

Airborne sound insulation The technical speciﬁ cation gives class ratings for three situations: 1. Between habitable rooms in a dwelling and rooms outside the dwelling in all directions. 2. From common stairwells or access areas into habitable rooms in dwellings, where there is an entrance door in the separating wall. 3. From premises with noisy activities into habitable rooms in dwellings.

• airborne sound insulation;

• impact sound insulation;

• airborne sound insulation of building envelopes against outdoor noise from traﬃ c, industry or other sources;

With respect to building regulations the ﬁ rst category is the most important. The classes of airborne sound insulation for separating walls and ﬂ oors are given in Table 1 of the standard and are:

• sound pressure levels in the dwellings from service equipment; and

Acoustic classes The classes A to F specify diﬀ erent levels of acoustic conditions in

Below: Table 1: Airborne sound insulation – Class limits

• reverberation time or ratio of the equivalent sound absorption

Type of space Class A Class B Class C Class D Class E Class F

D n T ,50 ≥ 58 D n T ,50 ≥ 54 D n T, A ≥ 52 D n T, A ≥ 48 D n T, A ≥ 44 D n T, A ≥ 40

Between habitable rooms in a dwelling and rooms outside the dwelling in all directions.

Note 1 – Diﬀ erent descriptors are applied to reﬂ ect use of diﬀ erent frequency ranges and weightings. Instead of DnT,A, DnT,w may be applied, if 2 dB is added to the limit value. If D n T,A is applied instead of DnT,50, 2 dB should be added to the limit value of DnT,50. For comparison between descriptors, see ISO 12354-1. (Table extract and note reprinted from ISO/TS 19488:2021 Acoustics – Acoustic classiﬁ cation of dwellings.)

Applying the Note 1 corrections speciﬁ ed above the classes for airborne sound insulation are shown in Table 1b (below):

Type of space Class A Class B Class C Class D Class E Class F

D n T ,w ≥ 62 D n T ,w ≥ 58 D n T,w ≥ 54 D n T,w ≥ 50 D n T,w ≥ 46 D n T,w ≥ 42

Between habitable rooms in a dwelling and rooms outside the dwelling in all directions.

As an example, 56 dB D nT,w is the minimum airborne sound insulation in Section 5: Noise of the Building Standards (Scotland) which would be Class C. It is more diﬃ cult to compare these values with the performance requirements of Approved Document E (England) such as the minimum 45 dB D nT , w + C tr. However, if the typical C tr. value is -5 dB 1 for a blockwork cavity separating wall, then this would be Class D.

For higher performance requirements such as found in Section 7: Sustainability (Scotland) where ‘gold’ level is min 60 dB D nT,w, this would equate to Class B.

2. For habitable rooms in dwellings from: — common stairwells or access areas; — balconies or terraces or bath rooms not part of the same dwelling. 3. For habitable rooms in dwellings from adjoining premises with noisy activities. With respect to building regulations the ﬁ rst category is the most important.

Above: Table 1b: Conversion to D n T ,w airborne sound insulation – Class limits

Impact sound insulation The standard gives class ratings for three situations: 1. For habitable rooms in dwellings from other dwellings in all directions.

P34

1 See Defra Contract NO0234, ‘An investigation into the eﬀ ect of historic noise policy interventions’ Annex 4 – Building Regulations published in 2012 .

ACOUSTICS BULLETIN MAY / JUNE 2021 33

FEATURE

The classes of impact sound insulation for separating ﬂ oors are given in Table 2 of the standard as follows (below):

Type of space Class A Class B Class C Class D Class E Class F

Between habitable rooms in a dwelling and rooms outside the dwelling in all directions.

L’ nT,w ≤ 46 and L’ nT,50 ≤ 50 1

L’ nT,w ≤ 50 and L’ nT,50 ≤ 54 1 L’ nT,w ≤ 54 L’ nT,w ≤ 58 L’ nT,w ≤ 62 L’ nT,w ≤ 66

Note 1 – Experience has shown that when applying the low-frequency rating, potentially disturbing high frequency sounds are not rated appropriately, and for this reason, two descriptors are applied in order to account for both hard ﬂ oor (mid frequency) impact sounds as well as low frequency footstep sounds. The limit values for L’nT,w are 4 dB lower than those speciﬁ ed for L’nT,50. For comparison between descriptors, see ISO 12354-2. (Table extract and note reprinted from ISO/TS 19488:2021 Acoustics – Acoustic classiﬁ cation of dwellings.)

Above: Table 2 : Impact sound transmission – Class limits

This would result in the building regulations being Class D (Scotland) and Class E (England).

Airborne sound insulation of façades The classiﬁ cation of airborne sound insulation against exterior noise is somewhat diﬀ erent to the procedures normally adopted in the United Kingdom. The minimum ‘class’ values for sound insulation are shown in Table 3, which is reproduced below, for a speciﬁ c environment

as characterised by L den for the relevant outdoor sound sources. L den , is the A-weighted free ﬁ eld sound level for the relevant outdoor sound sources with weighting of the day, evening, night period over the frequency range from 50 Hz to 5,000 Hz as deﬁ ned in the END (European Noise Directive) for outdoor sound.

In case the dominant sources of noise on the outside has a diﬀ erent spectrum than C tr , a more relevant spectrum adaptation term than C tr is to be applied to calculate the weighted single number, D nT,A,tr, in order to have similar sound pressure levels in the habitable rooms. The index ‘tr’ may then be replaced by a more descriptive index for the actual type of source.

Below: Table 3: Sound insulation in dwellings against exterior noise – Class limits 1, 2

Type of space Class A Class B Class C Class D Class E Class F

Façades and roofs of habitable rooms in dwellings; in speciﬁ c environment with sound sources characterized by L den

D n T ,A,tr ≥ L den - 20 D n T ,A,tr ≥ L den - 24 D n T ,A,tr ≥ L den - 28 D n T ,A,tr ≥ L den - 32 D n T ,A,tr ≥ L den - 36 D n T ,A,tr ≥ L den - 40

1 The sound insulation values are expressed as a weighted standardised sound level diﬀ erence with a spectrum adaptation term for road traﬃ c noise. For other types of sound source than road traﬃ c noise, DnT,A,tr shall be determined from the relevant level and spectrum of the sources. D nT,w + C tr,50–3150 may be used, where low frequency sound inﬂ uences the indoor sound pressure level. e.g. where the sound comes from mechanical equipment placed outside the building. 2 D nT,A,tr ≥ 30 dB applies as a minimum requirement to classes A–D.

(Table and notes reprinted from ISO/TS 19488:2021 Acoustics – Acoustic classiﬁ cation of dwellings.)

During the development of this standard there was considerable debate about the appropriateness of using Lden in this application because it is not what might be measured at any particular site. It represents the average over a 24-hour period rather than what the actual occupants will experience at various times throughout the day. It is important to note that ISO standards are developed on a consensus basis and most acousticians will not necessarily

agree with all the contents of any particular standard. In this case the standard says: “All requirements for a class shall be fulﬁ lled in order to obtain a certain class designation. A classiﬁ cation can be made for a whole residential building, only if all dwellings in the building fulﬁ l the class criteria. Dwellings in a building can also be assigned diﬀ erent classes. Classiﬁ cation can also be made for an individual dwelling or even for an individual room or a

speciﬁ c characteristic, e.g., airborne sound insulation, separately. The classiﬁ cation applies as long as there are no adverse changes in building constructions or environment. If such changes have occurred, e.g., by new roads nearby, the classiﬁ cation should be reconsidered.” (This extract is reprinted from ISO/ TS 19488:2021 Acoustics – Acoustic classiﬁ cation of dwellings.) This was a compromise and it is possible to not use some of the speciﬁ c characteristics. P36

34 ACOUSTICS BULLETIN MAY / JUNE 2021

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Sound from building service equipment The maximum values of the classes for A-weighted time-averaged, or the maximum sound pressure levels due to service equipment are shown in Table 4 (below).

Type of space and sources 1,2 Quantity Class A Class B Class C Class D Class E Class F

In habitable rooms in dwellings from outdoor and indoor service equipment producing continuous sound

L A,eq,nT ≤ 22 ≤ 26 ≤ 30 ≤ 34 ≤ 38 ≤ 42

In habitable rooms in dwellings from outdoor and indoor service equipment producing intermittent or irregular sound, from neighbouring spaces

L AF,max,nT 3 ≤ 26 ≤ 30 ≤ 34 ≤ 38 ≤ 42 ≤ 46

1 Requirements relate to sounds that occur more than occasionally due to service equipment in neighbouring dwellings, equipment serving the whole building and service equipment within the dwelling for normal ventilation/heating/cooling. 2 Sound with tonal components may be perceived more annoying and may be subject to national regulations. 3 L AS,max,nT may also be used, provided that 4 dB stricter limits (lower sound levels) are fulﬁ lled, i.e. the same as the L Aeq,nT.

(This table is reprinted from ISO/TS 19488:2021 Acoustics – Acoustic classiﬁ cation of dwellings.) Above: Table 4: Sound from building services equipment – Class limits Reverberation time Reverberation time was another somewhat contentious issue. At one point in the development of the standard the committee considered relegating this to an informative annex. The problem was to specify either measured

values or a calculated value of absorption. The maximum values for reverberation time and minimum values of equivalent sound absorption area in stairwells and access areas adjacent to habitable rooms are shown in Table 5 (below).

Below: Table 5: Reverberation time T and sound absorption A – Class limits

Type of space Class A Class B Class C Class D Class E Class F

1 In access areas (except common stairwells) 1 T ≤ 0,6 s T ≤ 0,9 s T ≤ 1,2 s T ≤ 1,5 s T ≤ 1,8 s T ≤ 2,1 s

2 In common stairwells 1, 2 T ≤ 0,9 s or A ≥ 0,45 × S ﬂ oor

T ≤ 1,2 s or A ≥ 0,35 × S ﬂ oor

T ≤ 1,5 s or A ≥ 0,25 × S ﬂ oor

T ≤ 1,8 s or A ≥ 0,20 × S ﬂ oor

T ≤ 2,1 s or A ≥ 0,15 × S ﬂ oor

T ≤ 2,4 s or A ≥ 0,10 × S ﬂ oor

(This table is reprinted from ISO/TS 19488:2021 Acoustics – Acoustic classiﬁ cation of dwellings.)

Note 1 – The limits for reverberation time are maximum values, and the limits for equivalent sound absorption are minimum values, in both cases for each of the octave bands 500 Hz, 1000 Hz and 2000 Hz.

Note 2 – For practical reasons, as an alternative to the requirement of a reverberation time in these type of spaces, a corresponding amount of equivalent sound absorption area according to EN 12354–6 has been added, using the equivalent absorption area A ≥ 0,16 V / T and an approximately 0,3 s longer T-value, compared to the ﬁ rst row.

36 ACOUSTICS BULLETIN MAY / JUNE 2021

Procedure B Procedure B is veriﬁ cation by ﬁ eld measurements only. This requires that 10% of the building separating walls and ﬂ oors etc are tested. The standard covers all the necessary detail on what to measure, relevant ISO standards, and what should be in a report. This article can only cover the highlights.

The compromise was to specify both measured values and calculated absorption values despite the fact that they may not necessarily be equal in many situations.

Acknowledgements The authors wish to acknowledge and thank, in particular, all the participants of ISO TC43/SC2/ WG29 committee for their considerable input and work over several years.

Veriﬁ cation of compliance Veriﬁ cation can apply to an entire residential building, an individual dwelling, a speciﬁ c habitable room or even a speciﬁ c acoustic characteristic, which are referred to as a ‘unit’. Two alternative veriﬁ cation procedures are described, Procedure A and B, and either procedure may be applied. When verifying the acoustic class of a unit, the general principle is that a suﬃ cient number of rooms should be selected for testing in order for the result to represent the unit and each relevant acoustic characteristic should be evaluated for this unit. Acoustic calculations and measurements are performed according to the relevant standards speciﬁ ed in the main body of this international standard. Unoccupied (unfurnished) rooms oﬀ er favourable measurement conditions, but the results are corrected to represent furnished rooms (as occupied). The persons or organizations that are appointed to make the relevant design calculations or performance estimations, visual inspections or measurements shall be qualiﬁ ed for the tasks. The contents of a report of acoustic classiﬁ cation are given in Annex A.3 of the technical speciﬁ cation.

About the authors: Philip Dunbavin is the Managing Director of PDA Ltd and a Fellow of the Institute of Acoustics. He is the current chairman of the BSI‘s overarching EH/1 committee on acoustics and serves on the ISO working group, WG29, which is responsible for the development of the classiﬁ cation scheme. He was convenor of WG1 (COST Action TU0901), which was responsible for the harmonisation of the descriptors and the development of the classiﬁ cation scheme.

Uptake It is important to note that this standard is in addition to Approved Document E (ADE) or Section 5: Noise of the Building Standards (Scotland) and does not replace them. All residential developments must still comply with these minimum airborne or maximum impact standards or approved document guidance. This technical speciﬁ cation may appeal to the high-end builders who are constructing houses and apartments for a market that targets signiﬁ cantly better than the ‘minimum standard’ provided by building regulations. This process is partly already available through the robust details process, the published credits for the previous Code for Sustainable Homes (CfSH), and the Section 7: Sustainability Scotland silver and gold performance levels. However, a future uniformity across the UK in approach for sound insulation criteria may also help architects, product manufacturers and developers who operate pan-UK. A key factor for all designers over the coming years will be the net zero ambitions for a construction project and the level of technical speciﬁ cations for non-energy areas and embodied carbon. It is likely that designers may take a judgement on whether an ‘A’ rating is still desirable if it conﬂ icts with the need to provide signiﬁ cantly enhanced speciﬁ cations, which may (not always) impact on net zero outcomes. It is not yet clear how many of the European countries may adopt or use the new classiﬁ cation scheme but it will be an interesting future factor to follow.

Professor Sean Smith is Chair of Future Construction and Director of Centre for Future Infrastructure, University of Edinburgh and a Fellow of the Institute of Acoustics. He has presented to CEN and ISO committees on future changes to sound insulation standards and is an acoustic advisor to Robust Details. He was convenor of WG3 of the 32 countries partnership (COST Action TU0901) reviewing future standards harmonisation and construction robustness.

Procedure A Procedure A is veriﬁ cation by calculations, visual inspections, and ﬁ eld measurements. This is a three-stage process: 1. I n the design stage of a building the performance can be calculated using the ISO 12354 series or from estimations from known typical performance. 2. In the construction stage of a building suﬃ cient visual inspections are conducted to ensure that elements are installed correctly. 3. In the completed building 5% of the building is to be ﬁ eld tested.

ACOUSTICS BULLETIN MAY / JUNE 2021 37

TECHNICAL CONTRIBUTION

Avoiding sleep disturbance and minimising carbon emissions through sustainable airport operations

Climate change will have far-reaching implications for the aviation sector if it does not address carbon emissions from aircraft operations. For airports to demonstrate that their operations are truly sustainable, they must also address other environmental challenges which impact on communities surrounding airports; such as noise. It is not appropriate to consider noise issues in isolation. Fully integrated and holistic solutions are needed for matters related to carbon management and community compensation.

By Colin Cobbing, Pinnacle Acoustic Consultants Limited colin@pinnacleacoustics.co.uk

his article explores if it is technically feasible and sustainable to avoid adverse eﬀ ects on sleep in communities exposed to aircraft noise. Before turning to steps that can be taken to minimise and avoid adverse eﬀ ects from sleep it will be necessary to explain how exposure to aircraft noise events can adversely impact on the health and quality of life of humans and what is meant by ‘objective sleep disturbance’.

eﬀ ects (e.g., self-reported chronic sleep disturbance). It is important to recognise that we as humans are not conscious of our own bodies when asleep and that noise can impact on our bodies and sleep patterns even though we might not be aware of it. It is for this reason that self-reported sleep disturbance is considered to be a poor indicator of sleep disturbance and associated health eﬀ ects. Nonetheless, self-reported sleep disturbance is an important indicator of community annoyance resulting from night-time operations. The gold standard for measuring sleep is polysomnography, which is the simultaneous measurement of (at least) brain electrical potentials (electroencephalogram, EEG), eye movements (electrooculogram, EOG) and muscle tone (electromyogram, EMG). The night is usually divided into 30 s epochs and a sleep stage (or awake) is assigned to each epoch based on typical patterns in the EEG, EOG and EMG according to standard criteria. Rapid eye movement (or REM) sleep is diﬀ erentiated from

non-REM stages S1 through to S4. Stages S3 and S4 (or N3) are also called deep or slow wave sleep. The deeper sleep stages (NREM stage 3 and 4 and REM sleep) are considered the most important in terms of the restorative eﬀ ects of sleep. The average sleep cycle lasts between 90 to 110 minutes and an individual experiences between four to six sleep cycles per night. It is usual for people to move between NREM sleep stages several times before undergoing REM sleep. The German Aerospace Centre (DLR) carried out a large ﬁ eld study on aircraft noise sleep disturbance using polysomnography 1 . It was found that the reactions of sleeping humans to noise cannot be diﬀ erentiated from spontaneous reactions using polysomnography. In the DLR aircraft noise study about 24 spontaneous awakenings on average were observed using electroencephalograms (EEG awakenings). Dr Mathias Basner conducted a review of the evidence and published exposure response relationships for road, rail and aircraft 2 . P40

1. Scientiﬁ c evidence on sleep disturbance There is clear evidence that chronically disturbed or curtailed sleep is associated with a number of negative health outcomes. Studies have shown that noise can aﬀ ect sleep in terms of immediate eﬀ ects (e.g., arousal responses, sleep state changes, awakenings, body movements, total wake time, autonomic responses), after-eﬀ ects (e.g., sleepiness, daytime performance, cognitive function) and long-term

38 ACOUSTICS BULLETIN MAY / JUNE 2021

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TECHNICAL CONTRIBUTION

Basner’s equation for the probability of noise-induced awakenings for an aircraft noise event is:

Figure 1

Equation 1: Probability of Wake or S1 = −3.0918 − 0.0449 – L AS,max + 0.0034 –(L AS,max ) 2

Probability of awakening (%)

This relationship is shown in the ﬁ gure on the right.

The long-term health consequences of noise-induced EEG awakenings are not fully understood. There are some suggestions that humans may be able to adapt to a certain level of noise-induced awakening without negative health consequences. In this context, it is necessary to consider the level of impact on sleep resulting from noise-induced EEG awakenings in comparison to those that would naturally occur in the absence of noise. For example, one additional awakening per night is a value that has been suggested by Basner et al. 1 in the health protection scheme for the Leipzig/Halle airport in Germany. To manage the risk of sleep disturbances associated with aircraft noise. Basner et al recommended that:

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 6 1 62 6 3 64 65

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

-1

L AS,max

Above: Figure 1: Probability of additional sleep stage changes to awake or S1 in a 90 s time window following a noise event onset depending on the maximum indoor sound pressure level (L AS,max ) for aircraft sound events

Number of movements needed to induce one additional awakening

L AS,max (indoors) Probability of sleep stage change to awake or S1 (%)

38 0.1 896

39 0.3 304

40 0.6 181

41 0.8 128

and number of events needed on average per night* over a year to induce one additional awakening. There is nothing to suggest that one additional awakening on average per night is the correct number for the protection of health. It was simply suggested as a precautionary concept based on the fact that one additional awakening on average per night is a small number compared to the number of spontaneous awakenings that occur per night. Basner has, however, suggested that the noise-induced awakenings could have more of a detrimental eﬀ ect on sleep quality compared to spontaneous awakenings 2 . Within the context of policy on sustainable development it would be necessary to consider both the economic beneﬁ ts associated with night ﬂ ights, the positive eﬀ ects on health and quality of life resulting from that economic activity and the negative eﬀ ects on health and quality of life resulting from aircraft noise at night. The Basner concept could provide a useful and cautious starting point for any noise protection policy. P42

42 1.0 98

43 1.3 79

44 1.5 66

• On average there should be less than one additional EEG awakening induced by aircraft per night, and

45 1.8 56

46 2.0 49

47 2.3 43

48 2.6 39

• Awakenings recalled the following morning should be prevented as much as possible, and

49 2.9 35

50 3.2 32

51 3.5 29

• There should be no relevant impairment to the process of falling asleep again.

52 3.8 27

53 4.1 25

54 4.4 23

In order to prevent recalled awakenings Basner et al proposed that the maximum noise level inside the bedroom should not exceed 65 dB. The impairment to the process of falling asleep again is suggested to be dependent upon the number of events and the time interval between events. Table 1. (right) Shows the probability of additional sleep stage changes to awake or S1 in a 90 s time window following a noise event at a speciﬁ c maximum indoor sound pressure level (L AS,max )

55 4.7 21

56 5.1 20

57 5.4 19

58 5.7 17

59 6.1 16

60 6.5 15

61 6.8 15

62 7.2 14

63 7.6 13

64 8.0 13

65 8.4 12

* The night period is typically deﬁ ned as the period between 23:00 and 07:00

40 ACOUSTICS BULLETIN MAY / JUNE 2021

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TECHNICAL CONTRIBUTION

2. Cardiovascular health and noise It has been shown that long-term exposure to transportation noise may increase the risk of heart disease; individuals exposed to higher levels of noise are exposed to the greater risk, especially at daytime noise levels outdoors above 60 dB. There are uncertainties on the relative importance of exposure during the day and night periods and the importance of sleep disturbance as a mechanism that leads to cardiovascular disease. Biological models on cardiovascular disease would suggest that sleep disturbance is important in terms of cardiovascular health 3 .

3. Noise abatement operational procedures, and 4. Operating restrictions. This serves as a good framework for considering the steps that can be taken to avoid adverse eﬀ ects of aircraft noise on sleep.

In 2011 the European Commission’s High-Level Group on Aviation Research published a vision for aviation in 2050 called ‘Flightpath 2050’ 5 . The associated noise goal is equivalent to a 15 dB reduction in cumulative noise (combined take-oﬀ , side-line and approach noise level established using the ICAO noise certiﬁ cation procedures) by 2050 relative to year 2000 technology (the equivalent of a 0.3 dB improvement per aircraft operation per year). Achieving reductions of this scale in the future will require signiﬁ cant developments in low-noise technology, probably associated with novel aircraft conﬁ gurations such as blended wing

Technology Since ICAO started to set noise emission limits for civil jet aircraft, signiﬁ cant cumulative reductions in aircraft noise emissions have been achieved over the past 50 years or so as a result of increases in engine bypass ratio, continuing improvements in noise reduction technologies and reduced aircraft weight.

Below: Figure 2 : Historic trend in aircraft noise reduction (reproduced from Sustainable Aviation Noise Road-Map) 4

3. Other determinants aﬀ ecting health and quality of life Noise is one of a number of factors or conditions aﬀ ecting sleep and the wider health and well-being of people whilst indoors. These include ventilation, overheating, excessive cold, security, internal air quality, damp and mould growth, lighting and connectivity with the external environment. A number of these factors are closely interrelated, for example having to keep windows closed to reduce noise levels indoors could result in poor indoor air quality and overheating. It is important therefore to consider all the factors associated with living conditions to understand the overall eﬀ ect on health and quality of life. Factors aﬀ ecting health, wellbeing and comfort are also closely related to the way in which people use buildings and this could also have signiﬁ cant implications in terms of heat conservation, energy use and carbon emissions. All of these factors need to be considered to address the challenges of climate change.

Evolutionary designs deliver 0.1dB reduction per point per year

Cumulative Noise Levels rlative to Chapter 3 (EPNdB)

With periodic revolutionary designs (higher engine bypass ratios), 0.3dB reduction per year is achieved

-10

BPR: < 2 BPR: 2 to 7 BPR: 7 to 10

-20

-30

1960 1979 1980 1990 2000 2010

Year

4. Steps that can be taken to avoid the adverse eﬀ ects of aircraft noise on sleep The International Civil Aviation Organization (ICAO) Balanced Approach to aircraft noise has four principal elements for managing aircraft noise: 1. Reduction of noise at source 2. Land-use planning and management

42 ACOUSTICS BULLETIN MAY / JUNE 2021

aircraft and aircraft conﬁ gurations that shield the engines when they ﬂ y overhead. It is worth noting that these trends are forecast using Estimated Perceived Noise Levels and may not necessarily reﬂ ect trends in L Amax levels.

approaches can deliver noise reductions at various distances away from the airport. Figure 3 (reproduced from the CAA) 6 shows the beneﬁ t of diﬀ erent landing operational measures at diﬀ erent distances from the runway threshold. The beneﬁ ts provided by operational procedures are incremental and do not tend to provide noise reductions that are, by themselves, necessarily noticeable or valued.

When considered on a cumulative basis however, operational procedures can provide important beneﬁ ts that contribute to an eﬀ ective noise management regime. If we consider landing aircraft as an example, Table 2 provides representative L Amax data as a function of aircraft height above ground for diﬀ erent groups of aircraft across three UK airports (Heathrow, Gatwick and Stansted). The Boeing 747-400 represents the 400 seat aircraft and the Airbus 380 represents the 500 seat aircraft. It is worth noting that the vast majority of remaining 747 aircraft operating in the UK were retired last year and that Airbus have stopped manufacturing the A380. The general trend is away from four engines to twin engines and the ﬂ eet mix for longer-haul aircraft is more likely to be dominated by the 250 to 350 seat groups. The 250 to 350 seat twin-aisle jets are therefore likely to be more representative of medium and long- haul ﬂ ights landing at night. It can be seen that the highest L Amax for these groups of aircraft landing at 1,000 feet and above is on average 84 dB. For departures the equivalent level is 92 dB. This suggests that the vast majority of people exposed to aircraft noise will not experience average L Amax values greater than 90 dB at night.

Below: Figure 3: Comparison of beneﬁ ts of individual arrival noise measures (reproduced from CAP1165) 6

Aircraft performance Displaced landing thresholds and operational procedures such as continuous descent approaches, low power low drag, steeper climb out proﬁ les and steeper landing

Continuous descent operation

4.5

Low power / low drag

Reduced landing ﬂ ap

3.5

Noise beneﬁ t (dBA SEL)

2.5

1.5

0.5

0 2 4 6 8 10 12 14 16 18 20 22 24

Distance from current runway threshold (nm)

P44

ACOUSTICS BULLETIN MAY / JUNE 2021 43

‘Note benefit (SBA SEL) iecbnidiehinnedeneaaGn

TECHNICAL CONTRIBUTION

500 seat 4-eng jet (A380)

400 seat 4-eng jet (B747)

300-350 seat twin- aisle jet

250 seat twin-aisle 2-eng jet

125-180 seat single-aisle 2-eng jet

Height (ft) Turboprop 50 seat regional jet 70-90 seat regional jet

1,000-2,000 79-70 73-63 77-67 77-69 84-74 83-73 86-77 85-78

2,000-3,000 70-66 63-56 67-61 69-64 74-68 73-67 77-71 78-72

3,000-4,000 66-64 56-55 61-57 64-61 68-64 67-63 71-67 72-68

4,000-5,000 64-62 57-56 61-59 64-60 63-60 67-64 68-65

5,000-6,000 62-61 56-55 59-57 60-58 60-57 64-61 65-62

6,000-7,000 61-59 57-56 58-56 57-56 61-59 62-60

7,000-8,000 59-57 56-55 56-55 56-56 59-57 60-58

8,000-9,000 57-57 56-55 57-56 58-56

9,000-10,000 57-56 56-56 56-55

10,000-11,000 56-55 56-55

Airspace design As explained earlier, disturbance to sleep at a speciﬁ c location is strongly dependent on the number of overﬂ ights and the maximum noise level of individual events. Airspace modernisation and the introduction of performance based navigation (PBN) has the potential to signiﬁ cantly reduce sleep disturbance because the greater certainty of an aircraft’s position and 4D ﬂ ight path can be used to maximise dispersion. For example, by allowing aircraft to ﬂ y a larger number of diﬀ erent arrival and departure routes, aircraft can be spread more evenly/fairly across a larger geographic area. For two or more runway airports this dispersion could be maximised even further if the movements could be distributed across the runways. It is worth acknowledging that greater dispersion may result in marginally longer ﬂ ight paths below 7,000 ft, which could result in a fuel burn/CO 2 disbeneﬁ t. provided this disbeneﬁ t is not disproportionate however, it will be in line with current government altitude-based environmental priorities. Maximising dispersion will only work for communities situated further away from airports and

Using the probability of awakening relationship given in equation 1 and allowing 15 dB attenuation for a partially open window and assuming an external L Amax of 60 dB; the maximum number of aircraft noise events (ANEs) inducing one additional awakening on any given night would be 56 movements. The number of ANEs would reduce to 21 if the external L Amax increased to 70 dB. Conversely, there would be no noise-induced awakenings if the if the external L Amax decreased to 52 dB. These examples are based on simple assumptions for a partially open window and numbers of events over an individual night. The number of additional awakenings over a year will depend on the spatial distribution of aircraft and the amount of time that windows are opened over the period of a year. Awakening contours can, however, be calculated using typical ﬂ ight path information averaged over a year. It may also be possible to calculate awakening contours based on internal noise levels derived for diﬀ erent land use patterns and occupancy data about the amount of time windows are opened and closed during the night.

not for areas closer to airports, located under ﬁ nal approach paths i.e., where aircraft need to line up parallel with the runway during the later stages of landing, or immediate take-oﬀ before aircraft can start to vector. Even so, it is possible that PBN could shorten the distance required for ﬁ nal approach compared to ground-based navigation methods and deliver more departure route options. It can be seen from Table 2 that an aircraft landing from a height greater than 10,000ft, at a considerable distance from the airport has the potential for causing some disturbance to sleep quality. At these altitudes, however, the numbers of overﬂ ights are unlikely to reach a point where the number and level of events would cause adverse eﬀ ects on sleep. At 5,000ft and above, one additional awakening could be avoided on average per year if the number of events was below 56 movements on average per night (assuming 250 to 350 twin jet aircraft). Above 3,000ft this would reduce roughly to 20 movements on average per night. Aircraft are likely to be on ﬁ nal approach at altitudes between 2,000ft and 4,000ft. The

Above: Table 2. Arrivals L ASmax levels by aircraft grouping (reproduced from NATS) 7

44 ACOUSTICS BULLETIN MAY / JUNE 2021

actual distance will depend on local factors and the type of navigation. It can be seen from this rough exercise how airspace design could provide a useful means of mitigating sleep disturbance before the aircraft start to join ﬁ nal approach. Variability in noise exposure at night is an area of sleep disturbance that is not well understood. There is some evidence, however, to suggest that large variability in night- time operations could increase objective sleep disturbance 8 . It will not always be practical to avoid variability because the direction in which aircraft need to land and take oﬀ is primarily inﬂ uenced by the wind speed and direction. Measures that can be used to minimise variance should be carefully considered. For example, for airports with more than one runway it may be better to consistently distribute aircraft movements across

the runways rather than rotate movements between the runways on diﬀ erent nights or diﬀ erent times of the night. The industry is exploring ways in which improved navigation accuracy can deliver predictable respite from noise during the day when aircraft noise is perceptible. Respite measures could help to improve daytime annoyance if it is implemented eﬀ ectively. It is important to recognise, however, that the mechanisms associated with daytime annoyance are materially diﬀ erent from those associated with objective sleep disturbance. There is a possibility that the introduction of predictable periods of respite during the night could actually make objective sleep disturbance signiﬁ cantly worse. It is important therefore, that airspace management measures used to reduce night-time impacts are

considered separately from those deployed when people are awake. Daytime respite arrangements could potentially constrain airspace designs during the night and vice versa. It is important therefore that the overall eﬀ ects on health and quality of life are considered using the best available scientiﬁ c evidence so that the best balance between daytime and night-time measures can be achieved.

Land use planning Land use planning has typically been viewed as zoning around airports. Such measures have not been particularly eﬀ ective, not least because there is a high demand for housing and other development around airports. Airports have implemented large- scale community sound insulation schemes, where existing windows are treated with secondary P46

ACOUSTICS BULLETIN MAY / JUNE 2021 45

TECHNICAL CONTRIBUTION

glazing or they are replaced with new double-glazed windows incorporating laminated glass. There can be signiﬁ cant drawbacks associated with such measures because they rely on windows being closed to be eﬀ ective and having to keep windows closed can give rise to negative eﬀ ects on indoor air quality, overheating and other factors aﬀ ecting wellbeing. Supplementary ventilation is normally provided as part of sound insulation packages but these might not always be suﬃ cient to avoid potential overheating and tend to be unpopular because residents feel they are unsightly, or make unwanted noise. Supplementary ventilation is also provided to mitigate the eﬀ ects of having windows closed, but there is a lot of evidence that people still prefer to keep windows open in high noise exposure areas for a variety of reasons that are not fully understood. Innovative window designs can overcome a lot of the drawbacks associated with sound insulation schemes. An example of this is the Hafencity window, which can achieve an Rw of 46 dB with windows in a partially open position and, at the same time, provide reasonable levels of passive ventilation [9] . The actual level of attenuation will depend on the frequency spectrum of the sound and the direction of the incident sound. The Rw is a reasonable measure of the level of attenuation for maximum noise levels from aircraft noise events. Levels of attenuation in the order of 45 dB can be used to reduce maximum noise levels from 90 dB outside the building to 45 dB or lower inside bedrooms, which is considered to represent a good acoustic design target in the UK

for maximum noise levels 10 . It can therefore be seen that innovative window systems can be used to avoid sleep disturbance from aircraft noise events for the majority of noise exposure cases found around airports, but without the negative eﬀ ects normally associated with having sealed up façades. Such measures would also provide wider beneﬁ ts in terms of health and quality of life because the sound insulation packages will reduce noise levels indoors from other sources of transportation noise. The beneﬁ ts associated with retroﬁ t schemes could be enhanced further if the schemes were designed to minimise carbon emissions and improve other aspects of health and quality of life in addition to noise. For example, retroﬁ t measures that improve thermal insulation would reduce the adverse health eﬀ ects associated with cold temperatures. Measures used to provide shading could help to minimise overheating during summer months. The UK Government recently attempted a scheme to improve thermal insulation and energy eﬃ ciency in homes in order to address climate change. This scheme has been seen as a failure and this may be explained, in part, by structural issues associated with the scheme and the renewables sector. Such schemes would be far more eﬃ cient and eﬀ ective if airport operators worked in partnership with government, local authorities and other agencies involved in reducing carbon emissions to co-ordinate or even unify the diﬀ erent retroﬁ t schemes. More importantly, such schemes could provide greater social value if the goals were widened to improve

health and quality of life, noise and sustainability performance. In this way, the value of retroﬁ t schemes could be signiﬁ cantly enhanced compared to the beneﬁ ts of retroﬁ t schemes that solely aim to reduce noise or carbon emissions. Innovative window and façade systems can also provide signiﬁ cant advantages in the design of new noise sensitive development around airports and overcome current design shortcomings i.e., only achieving good internal noise design criteria with windows closed. The windows can be designed as part of a total solution for good acoustics, ventilation and overheating using passive ventilation techniques. This could help to avoid dependencies on mechanical cooling and minimise energy consumption, thereby minimising carbon emissions.

Evidence-based decision-making A number of policies and intervention strategies for night- time noise are based on the L Aeq parameter. Reducing the number of ANEs at night by 50% whilst keeping the L Amax value unchanged would mean that the energy equivalent continuous sound level L Aeq will decrease by 3 dB. Criteria based on the L Aeq parameter would therefore signify that the eﬀ ects of aircraft noise on sleep are simultaneously diminished by 50%, an example of this being the number of awakenings induced by aircraft noise is halved. This is not consistent, however, with the relationship for the probability of noise-induced awakenings. Awakening contours could provide valuable evidence that could be used to inform decision-making. Night-time restrictions are applied at most European airports P48

46 ACOUSTICS BULLETIN MAY / JUNE 2021

ACOUSTICS 2021

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TECHNICAL CONTRIBUTION

e.g., UK aircraft noise classiﬁ cation (QC) and movement number limits. EU Regulation 598 (2014) is based on the ICAO Balanced Approach and sets the rules for the introduction of noise-related operating restrictions at EU airports. To ensure that noise management measures are sustainable, regulations require that noise operating restrictions be only applied as a measure of last resort and only after thorough consideration of the other measures of the balanced approach described above. This consideration must include a thorough evaluation of the cost-eﬀ ectiveness of the noise mitigation measures. Cost- eﬀ ectiveness is typically evaluated using noise impact analysis (see for example the impact assessment for night ﬂ ight restrictions at the designated airports is on UK Government website: https://tinyurl. com/ysh24dzb ) These assessments do not consider the eﬀ ectiveness of the noise intervention measures on health and quality of life; this is because there is little or no robust quantitative evidence on the eﬀ ect of interventions on health and quality of life. This situation could, however, be easily resolved and would not necessarily require large, expensive studies. Before-and-after studies provide a reliable means of measuring

and quantifying changes in health and quality of life resulting from diﬀ erent types of intervention, which are typically deployed by airport operators to mitigate the eﬀ ects of aircraft noise. The application of standardised methodologies to conduct before-and-after studies would allow the systematic evaluation and comparison of diﬀ erent intervention measures in terms of their eﬀ ectiveness to improve health and quality of life. The application of standardised methodologies would also enable evidence obtained from relatively small case studies to build towards a larger body of evidence that can be used to inform decision- making. It follows from this that it may not always be necessary to spend signiﬁ cant amounts of money on large and powerful research studies. What is needed most is for the aviation sector to co-operate and use standardised methods and approaches to study the relative eﬀ ectiveness of diﬀ erent types of intervention and then to pool that information so that the data can be systematically analysed.

Such relatively simple steps could bring about a step change in informing decisions on the most sustainable means of controlling and mitigating the eﬀ ects of aircraft noise.

Conclusions This article illustrates how airport operators and those responsible for land use planning around airports can implement noise control strategies that will sustainably avoid adverse eﬀ ects on sleep. It goes further to demonstrate how noise management strategies can be developed to: • Provide wider beneﬁ ts on health and quality of life and build social value for communities living and working around airports, and • Oﬀ set carbon emissions from aviation.

Finally, recommendations are made to drive the changes needed to develop and build the evidence base in order to improve decision- making on the cost-eﬀ ectiveness of diﬀ erent noise management interventions and combinations of interventions.

Acknowledgements I would like to thank Will Martin and Brendan Creavin for reviewing the article and providing useful comments.

References 1 M. Basner, A. Samel, U. Isermann (2006). Aircraft noise eﬀ ects on sleep: Application of the results of a large polysomnographic ﬁ eld study. J Acoust. Soc. Am. 2 M. Basner and S. McGuire. (2018) WHO Environmental Noise Guidelines for the European Region: A Systematic Review on Environmental Noise and Eﬀ ects on Sleep. International Journal of Environmental Research and Public Health. 3 World Health Organisation (2011) Burden of disease from environmental noise, Quantiﬁ cation of healthy life years lost in Europe. 4 Sustainable Aviation. Noise Road-Map. www.sustainableaviation.co.uk . 5 European Commission. (2011). Flightpath 2050 Europe’s Vision for Aviation Report of the High Level Group on Aviation Research. EUR 098 EN. 6 CAA (2014) Managing Aviation Noise. CAP1165. 7 NATS. Representative aircraft Lmax data. (2019) https://www.nats.aero/environment/aircraft-noise/representative-aircraft-lmaxdata/ 8 S. Fidell; B. Tabachnick; V. Mestre and L. Fidell. (2013) Aircraft noise-induced awakenings are more reasonably predicted from relative than from absolute sound exposure levels. J. Acoust. Soc. Am. 134 (5), November 2013. 9 W. Von Trotha (2019). Fresh Air and Silence - Maximizing the Potentials of Sound Insulation for Opened Windows. Internoise. 10 Professional Practice Guidance on Planning and Noise for New Residential Development (May 2017). CIEH; IOA and ANC.

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Are all meters equal? We subject a range of low-cost meters claiming to meet IEC 61672 to a periodic test to see how well they performed.

By John Campbell and Martin Williams

It can be tempting to buy the cheapest tool for the job, especially if it claims to meet all the relevant requirements. But can these claims be trusted, should the buyer take these statements at face value or with a heavy pinch of salt? Six meters were randomly selected and tested at two independent, accredited ISO 17025 UKAS laboratories. All six meters failed at least one test, with a number failing multiple tests and basic requirements for providing the relevant information to perform a periodic test. This may seem a bit strange as a contribution to a technical paper in a learned journal as they are not the tools that a professional would choose. They will, however, come across instruments in use by people who have acoustics as a secondary or tertiary job function who may well have chosen instrumentation that is marked with the established

standard numbers because of price. With acoustic measurements, the important factor is that they are ﬁ t for purpose; if the objective is to set up a domestic hi-ﬁ then any sound level indicator would do. However, if a meter is to support a statutory nuisance claim or part of a hearing conservation programme then the measurement must be to a certiﬁ able standard with a speciﬁ ed level of accuracy to provide comfort and a reasonable level of uncertainty that the measured data is sampled accurately. The measuring instrument is a key element of this uncertainty so for any measurement that is in support of statutory or regulatory requirements its performance must be well understood. The International Standard BS EN IEC 61672 covers sound level meters; it speciﬁ es what they should do (the speciﬁ cation, part 1) tests that are design related (pattern evaluation,

part 2) and tests that are use related (periodic veriﬁ cation, part 3). • 1. Speciﬁ cation: This sets out what the instrument must do and how accurately these objectives are to be realised. It allows for two classes of instruments, class 1 (precision) and class 2 (general purpose). Both have the same design goals, but wider tolerances are allowed for class 2 instruments. It is the manufacturer’s responsibility. • 2. Pattern evaluation: Here, fundamental matters are dealt with concerning how well the speciﬁ cation has been realised. In addition, the performance over the wide range of environments, i.e., anywhere humans live or work, as well as the eﬀ ects of electromagnetic interference; all of these functions need very specialised facilities to verify. In addition, the acoustic eﬀ ects of the instrument housing and front-end accessories such as windscreens need to be veriﬁ ed. This will provide the user with correction information to allow for regular calibration and give a full understanding of how the instrument performs in the ﬁ eld. Again, the manufacturer’s responsibility but the data should be conﬁ rmed by testing at an independent national laboratory. • 3. Periodic veriﬁ cation: Sometimes referred to as ‘calibration’ is normally a biennial check based on a restricted range of parameters that are designed to show any drift or damage during use. These tests are carried out at close to reference conditions and make use of correction data conﬁ rmed during the pattern evaluation. This is the user’s responsibility and for legal metrology applications carried out by an accredited laboratory. P52

Below: Free-ﬁ eld acoustic testing in an anechoic chamber

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50 ACOUSTICS BULLETIN MAY / JUNE 2021

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If both parts 2 and 3 have been carried out successfully then a calibration certiﬁ cate becomes a certiﬁ cate of conformance to the standard with results defendable in any court, tribunal or enquiry. If part 2 tests have not been carried out, any calibration certiﬁ cate will be endorsed with a statement making it clear that the meter may not comply with all the requirements of the standard and that it was a snapshot of the instruments performance at the time of the part 3 tests. The price of a sound level meter can range from a few tens of pounds to many thousands. The price may diﬀ er due to features within the instrument or because of the many expensive tests to conﬁ rm its ability to accurately measure noise have not been carried out. This article reports on a project that looked at a range of low-cost meters that claimed compliance to BS EN IEC 61672 class 2 standard in their sales literature. Six meters were purchased, from ﬁ ve diﬀ erent manufacturers, and submitted for UKAS accredited periodic testing at Campbell Associates and Cirrus Research calibration facilities to see how they performed to the restricted range of tests at reference conditions. Testing was against the Edition of IEC 61672-3 with which

also performed free-ﬁ eld tests. This resulted in greater variance in results between the two calibration facilities than would be expected if all relevant information was available.

each meter claimed conformance. Meters selected were priced between £75 to £375. Results were mixed, with most failing to provide suﬃ cient information to perform periodic test and all failing at least one test.

INSTRUMENTATION CORNER

Method of testing A number of the periodic tests are based on an electrical signal being applied to simulate an acoustic response. This is typically applied by removing the microphone and ﬁ tting an adaptor to the preampliﬁ er. Some of the meters had ﬁ xed microphones, and, as no test point was provided, the electrical signals were directly input into the meter as appropriate. IEC 61672 requires a sound level meter to have a removable microphone so any meter that does not have this capability immediately fails to conform to the standard. Other tests performed include sound pressure testing using a multi-frequency acoustic calibrator, measurement of the microphone self-noise and free-ﬁ eld testing in an anechoic chamber.

First impressions First impressions of all instruments selected were good, each meter was well packed and built. Only two of the six had the required information within the user manuals to enable periodic testing to be performed. The other four manufacturers were approached for this missing information and none were able to provide this data. The information on the corrections, test points and reference data are mandated by the standards and hence if not available the meter immediately does not comply with the standard and testing should not be performed. However, for the purposes of this paper, it was decided that each of the test laboratories would make their own estimates on the required information based on previous experience so that testing could continue. For this exercise, each laboratory performed testing as best they could, one laboratory performed electrical and sound pressure testing, whilst another

Test results The following tables provide a summary of the results for each instrument at both test facilities. Instruments have been labelled A to F. P54

Below: Acoustic pressure testing using a B&K 4226 multifunction calibrator

52 ACOUSTICS BULLETIN MAY / JUNE 2021

•

INSTITUTE AFFAIRS

INSTRUMENTATION CORNER

Test per IEC 61672-3 (2006) Edition 1 Instrument A Instrument D Instrument E Instrument F

Self-generated noise – clause10.2** Failed (1) Passed (1) Passed (2)

Passed (1) Passed (2)

Failed (1) Passed (2)

Acoustic frequency weightings – clause 11 Passed (1) Passed (1) Passed (1) Passed (1)

Electrical frequency weightings – clause 12 Passed (1) Failed (1) Failed (2)

Passed (1) Passed (2)

Weighting at 1 kHz – clause 13 Failed (1) Failed (2) Failed (1) Passed (2) Passed (1) Passed (2)

Failed (1) Failed (2)

Linearity – clause 14 Passed (1) Passed (1) Passed (2) Passed (1) Passed (2)

Failed (1) Failed (2)

Linearity (all ranges) – clause 15 Passed (1) Passed (1) Passed (2) Passed (1) Passed (2)

Passed (1) Passed (2)

Tone burst response – clause 16 Failed (1) Failed (1) Failed (2) Failed (1) Failed (2) Failed (1) Failed (2)

Overload indication – clause 18* Passed (1) Passed (1) Passed (2) Failed (1) Failed (2) Passed (1) Passed (2)

KEY: *Overload is optional for non-integrating instruments **Self-generated noise test is for indication and does not on its own, mean a meter does not comply, but may aﬀ ect linearity (1) Tests performed at Calibration facility 1 (2)Tests performed at Calibration facility 2

Test per IEC 61672-3 (2013) Edition 2 Instrument B Instrument C

Self-generated noise – clause 11** Passed (1) Passed (1)

Acoustic frequency weightings – clause 12 Passed (1) Passed (1)

Electrical frequency weightings – clause 13 Passed (1) Passed (2) Passed (1) Failed (2)

Weighting at 1 kHz – clause 14 Passed (1) Passed (1)

Typical results measured for frequency weighting are shown below. Typical failures recorded for units were failures above 2kHz and below 200Hz. Results are shown for electrical and free-ﬁ eld testing. Electrical testing should include manufacturers’ correction data to correct to free-ﬁ eld which was typically not provided, whilst correction data is not required for free-ﬁ eld testing. P56

Long-term stability – clause 15 Passed (1) Passed (1)

Linearity – clause 16 Failed (1) Passed (1)

Tone burst response – clause 18 Failed (1) Passed (1)

C-weighted peak – clause 19 Failed (1) Passed (1)

Overload indication – clause 20* Failed (1) Passed (1)

54 ACOUSTICS BULLETIN MAY / JUNE 2021

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Electrical frequency A & C weighting for, instrument D – Fail (no corrections provided)

Electrical frequency A & C weighting, instrument A – Pass (no corrections provided)

Free-ﬁ eld frequency A weighting, instrument D – Fail (no corrections required for free-ﬁ eld testing) Free-ﬁ eld frequency A weighting, instrument A – Fail (no corrections required for free-ﬁ eld testing)

i a rr or

Free-ﬁ eld frequency A weighting, instrument E – Fail (no corrections required for free-ﬁ eld testing) Free-ﬁ eld frequency A weighting, instrument F – Fail (no corrections required for free-ﬁ eld testing)

Of the six units, two failed linearity testing. Linearity tests are performed at the reference level range for meters with multiple ranges. The results shown are for

the reference range if identiﬁ ed in the manual. A second test is then performed at each range but limited to a single value in each range. Typical linearity failures at

the low end of a range are due to noise ﬂ oor of the instrument, however instrument A had an interesting step change halfway through the range. P58

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time weightings. A failure of this test will typically result in a meter reading low in real world situations and is typically the result of an over ﬁ ltered front end or insuﬃ cient sampling to detect noise bursts.

Most units failed tone burst tests, in many cases signiﬁ cantly. For example, a 2ms burst on meter D should have measured 79 dB, it measured 45.6 dB, giving a 33.4 dB error. Most tests performed

by IEC 61672 are based on stable sinusoidal test signals, whilst tone burst consist of a short burst of 4kHz sinusoidal signals, this test ensures the instrument measures complex signals correctly for fast and slow

INSTRUMENTATION CORNER

Electrical linearity – instrument A – Fail Electrical linearity – instrument B – Pass

Electrical linearity – instrument E – Pass Electrical linearity – instrument F – Fail

Burst Duration Meter A Meter B Meter C Tol (worst case) Exp Act Dev Exp Act Dev Exp Act Dev

ms dB dB dB dB dB dB dB dB dB dB

200 96.0 91.7 -4.3 126.0 93.9 -32.1 116.0 116.0 0.0 +/-1.3

2 79.0 56.3 -22.7 109.0 58.8 -50.2 99.0 98.9 -0.1 +1.3/-2.8

0.25 50.0 45.4 -24.6 100.0 47.9 -52.1 90.0 89.8 -0.2 +1.8/-5.3

Burst Duration Meter D Meter E Meter F Tol (worst case) Exp Act Dev Exp Act Dev Exp Act Dev

ms dB dB dB dB dB dB dB dB dB dB

200 96.0 96.8 0.8 96.0 88.0 -8.0 116.0 117.8 1.8 +/-1.3

2 79.0 45.6 -33.4 79.0 57.6 -21.4 99.0 80.0 -19.0 +1.3/-2.8

0.25 50.0 38.7 -31.3 50.0 41.1 -28.9 90.0 73.8 -16.2 +1.8/-5.3

58 ACOUSTICS BULLETIN MAY / JUNE 2021

Summary and conclusion All meters failed at least one test. Whilst one meter was close to passing all tests; others failed several tests, including linearity, frequency weighting and especially tone burst, which ﬁ ve of the six failed. Each meter was advertised as being compliant to IEC 61672, which would indicate it should meet the stringent requirements of this standard and should pass all the tests detailed of part 3. Meters were purchased new and immediately submitted to periodic testing per IEC 61672-3 at two test laboratories. Four units failed to provide required information in the user manual to enable a calibration

Above: Electrical testing a meter by using an adaptor ﬁ tted to the preampliﬁ er

check to be properly performed. In each case the manufacturer was contacted to request this information, and none were able to provide the correct information, with one acknowledging the requirement and changing their marketing information to remove any claims to IEC 61672. According to the standard, as this information was not available, testing should not normally be performed, but for this exercise tests were made and failure of the manufacturer to provide this information will mean some of the tests performed will not be accurate as additional uncertainties will have been introduced, as shown by some variance between individual

calibration facilities. However, it is unlikely the lack of this data would have resulted in failed tests becoming passes. The results show that a low-cost meter is (as might be expected) capable of providing a noise level indication, but also that a number of instruments that claim IEC 61672 compliance are not compliant. If an instrument is required for accurate noise measurements it is recommended that any claims of compliance are conﬁ rmed. This can be established by asking for evidence of type approval, typically in the form of a certiﬁ cate from a national metrology institute, and not by just relying on the marking on the sound level meter.

ACOUSTICS BULLETIN MAY / JUNE 2021 59

INSTITUTE AFFAIRS

2021 Conference programme

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ACOUSTICS 2021 11-12 October 2021 Crowne Plaza Hotel, Chester

HEAR FOR TOMORROW 30 March 2022 Royal Academy of Music, London Organised by IOA and Hearing Conservation Association

REPRODUCED SOUND 2021 16-18 November 2021 The Bristol Hotel, Bristol Organised by the Electroacoustics Group

ICUA 2022 20-24 June 2022 Grand Harbour Hotel, Southampton Organised by the Underwater Acoustics Group

INTER–NOISE 2022 20-24 August 2022 SECC, Glasgow

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60 ACOUSTICS BULLETIN MAY / JUNE 2021

FEATURE

Novel online conference held to promote mutual discipline awareness between acoustics and architecture students

On 4 March 2021 an online conference was held between London South Bank University (LSBU) Acoustics Group and the world-famous Architectural Association (AA) School of Architecture. 45 students and academic staﬀ from both institutions attended the afternoon event.

By Dr Luis Gomez-Agustina, Director for IOA courses at LSBU

Networking and feedback The conference was followed by a virtual audio visual tour of the LSBU acoustic laboratory facilities where the concept of reverberation and absorption were aurally demonstrated. After the tour, a friendly and virtual networking event was held for attendees to meet and greet. 28 attendees completed an online evaluation questionnaire designed to provide feedback on the event. 93% of those felt satisﬁ ed or very satisﬁ ed with the conference. 57.1% of the respondents believed that reciprocal appreciation and understanding of the two disciplines in the architectural design is very important while 42.9% believed that it is important. Almost three quarters (74%) felt that the conference had increased their understanding and awareness of the other discipline. My thanks go to AA School of Architecture teaching staﬀ and former LSBU MSc acoustics student, Laura de Azcarate, as well as LSBU Acoustics PhD student, Douglas Shearer, for assisting with the organisation and facilitation. It is hoped that this successful event will be repeated and even expanded in the near future with the participation of other national and/or international universities.

Left: The LSBU and AA online conference, ‘Acoustics in Architecture, Architecture in Acoustics’

he theme of the conference was ‘Acoustics in Architecture, Architecture in Acoustics’ and its aim was to improve the understanding of each other’s disciplines, enhance communication and promote collaborative work between acousticians and architects. The idea of this novel conference was formulated and developed by Dr Luis Gomez-Agustina in response to the impossibility this year to hold the face-to-face educational exchange events and site visits that both universities normally have in March.

and the Americas, were distributed in three breakout rooms with a balanced, mixed audience. Students from both institutions delivered a total of 17 presentations in the three parallel sessions moderated by academic staﬀ . Question and discussion time after each presentation was keenly utilised by the audience and provided the exchange of knowledge, ideas and insights sought by the organisers. In the concluding part of the conference there was time for further debate and ﬁ nal remarks from everyone gathered back together in the main room. The attendees were asked to vote online in real time for the best presentation of their break out room session. The winners have received a certiﬁ cate of achievement and an Amazon voucher as a prize. The conference was closed by showing a short, entertaining video which illustrated the eﬀ ects of reverberation in music and speech.

Exchange of knowledge The conference started with an introduction to the event in the main virtual room, to set the scene and create a participatory and relaxed atmosphere. Then attendees, calling in from locations around UK, Europe

For more information For an overview of the IOA Diploma in Acoustics and Noise Control at LSBU visit www.lsbu.ac.uk/courses/ course-ﬁ nder/acoustics-diploma

‘LSBU

ACOUSTICS BULLETIN MAY / JUNE 2021 61

FEATURE

Complex decision-making processes

In this article, Dani Fiumicelli looks at two cases where noise impacts were considered when deciding on development proposals nearby.

he ﬁ rst case is a planning appeal regarding the extension and conversion of a listed building in the centre of Wallingford, Oxfordshire, from a bank to eight ﬂ ats. The local planning authority had refused permission because the scheme did not adequately protect the future residents against noise from the adjoining theatre/cinema. The appeal was denied by a planning inspector, who was concerned that the future operation of an adjacent community theatre and cinema would be jeopardised by noise complaints leading to enforcement action. The inspector expressed concern that future occupants would be aﬀ ected by noise transmitted through a ﬂ anking wall and shared foundations, and doubted whether this noise could be realistically mitigated by amendment of the scheme before her. The source noise levels, and frequency of occurrence were debated extensively by the acoustic expert witnesses.

The council and the theatre considered that the higher crescendo system levels represented typical operating conditions, whereas the appellant argued that these were exceptional operating conditions, with the lower in-house cinema system levels being representative. The appropriate source noise levels required to trigger an assessment and/or design mitigation is a common area of disagreement in these cases. However, broad agreement was reached that disturbance was most likely from noise in the lower frequency octave bands. For example, it was agreed that internal design criteria for music noise levels in the proposed ﬂ ats were 40 dB LZeq, one minute in the 63Hz octave band and 30 dB LZeq, one minute in the 125Hz octave band, with a relaxation of 5 dB for non-habitable rooms e.g., toilets, kitchens and circulation spaces etc. The developer was prepared to accept a Grampian-style condition prohibiting development until further exploratory works and suitable noise mitigation had been secured. But the inspector rejected this approach, observing that if the foundations were shared; a substantially revised scheme would probably need to be resubmitted. This would mean a fundamentally diﬀ erent design might have to be submitted and this would require an entirely new application as this would not match the description of the scheme in the submitted planning application.

Case law means that conditions cannot be used to change the description of a permitted scheme, so it would be unlawful to leave these issues for ‘approval’ under a reserved matters condition i.e. ‘submit a scheme for approval etc’. Having regard to the agent of change principle of the PPG and adopting a precautionary approach to noise eﬀ ects, the inspector concluded the development would not provide satisfactory living conditions and statutory nuisance complaints could compromise the future of the community entertainment venue. This would conﬂ ict with the local plan policy and NPPF paragraphs 180 and 182 concerning noise mitigation in development. This case is Appeal A Ref: APP/Q3115/W/20/3249052, 4 Market Place, Wallingford, OX10 0EH.

Below: Dani Fiumicelli

Council’s “confused thinking” The second case is a High Court Judgment involving the clash of interests between a licensed premises and an adjacent housing development. In May 2000, the council granted permission for a change of use of the licensed premises from retail to the sale of food and drink on the ground ﬂ oor. To protect the conservation area and the amenity of neighbouring properties, the premises was required to close at midnight and not to play ampliﬁ ed music audible from the public highway.

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conditions.’ And the judge accepted that “ if a party wishes to vary the description of the development, then it must apply for a new planning permission.” Although the section 73 permission did not purport to change the original operative description of the development, it “sought to create the same eﬀ ect by imposing conditions inconsisent with it”, the judge added. On the face of it, the permission authorised the venue’s mixed use as a restaurant and drinking establishment, but the conditions attached to it purported to limit its use to that of a drinking establishment only. That inconsistency, said the judge, illustrated the council’s “ confused thinking .” Adding: “This has resulted in a permission which has had conditions imposed that are inconsistent with the original permission, purported to grant permission for something other than originally permitted and other conditions that were not consistent with an attempt to limit the new permission.” A requirement to ﬁ t a limiter to sound equipment was not included as a formal condition to the section 73 permission and the judge said it was “ perverse” not to have in place some means of enforcing compliance. The council should have refused, or deferred granting, permission until such compliance was secured. There also appeared to be substance in Parkview Homes’ complaints that it was irrational of the council to grant the permission without ﬁ rst performing noise tests, as recommended by its own environmental health department. Quashing the permission, the judge concluded: “This is a case of multiple errors in the decision- making process, including in the consultation process and in the substance of the permission issued. ” Chichester District Council did not contest Parkview Homes’ judicial review challenge to the section 73 permission and played no part in the hearing of the case. Sussex Inns Limited, however, defended the permission as an interested party.

The venue applied to vary the existing planning conditions under section 73 of the Town and Country Planning act 1973. This empowers local authorities to amend or remove conditions, but they are not entitled to amend any other part of the original permission. The application was granted with new conditions, amongst other things, allowing the venue to stay open until 2am from Thursday to Saturday and on New Year’s Eve and Christmas Eve. The council granted the permission despite objections from the developer of ﬂ ats next door to the venue, who were concerned about the impact of noise from the venue on residents. Furthermore, the EHO had advised that the under the previous permission the venue had operated at internal levels around 70 dBA, but in this case the ‘ level of sound transmission here is of a diﬀ erent order of magnitude where sound levels at source are approaching 100dB(A) with powerful bass tones … It is debateable whether any reasonable noise mitigation between the properties would be totally eﬀ ective in protecting new dwellings from intrusive noise from music levels found in a nightclub. … The protection of residents from excessive noise intrusion through the party wall is dependent on the adjacent property reverting to its lawful planning use and signiﬁ cantly reducing sound levels generated within to a level more

typically expected within a pub/ restaurant environment.’ The developer alleged that varying the original conditions ‘would intensify the noise impact’. They also argued that it was ‘unlikely that any level of mitigation could be provided to safeguard the amenity of residential units.’ Whilst noise was a primary driver in overturning the council’s decision, the High Court judge said the case “illustrates once again the diﬃ culties caused when a local planning authority purports to grant a permission under section 73 without suﬃ cient care as to its relationship with the parent permission”. The conditions attached to the section 73 permission were appropriate for a ‘drinking establishment’, rather than a bar and restaurant, and were therefore ‘inconsistent with the use speciﬁ ed in the description of development in the original permission.’ The judge upheld the developer’s argument that the revised conditions ‘derogated from the operative words’ of the 2000 permission and that the description of the development in the 2000 permission could not be amended under section 73, which ‘only permits the variation of

Case Citation:

Parkview Homes Ltd, R (On the Application Of) v Chichester District Council [2021] EWHC 59 (Admin) (15 January 2021) – can be viewed at https://www.bailii.org/

ACOUSTICS BULLETIN MAY / JUNE 2021 63

BRANCH NEWS

By C J Biggs BRANCH NEWS

Midlands Branch

Southern Branch

By Jack Richardson

An introduction to automotive NVH trim materials – AVA Consulting. In a well-attended presentation on 11 March 2021, Richard Crompton, Director at AVA Consulting, gave an interesting talk on an area of automotive acoustics that focused on the trim materials used in vehicles to control noise, vibration and harshness. Unfortunately, Richard’s business partner Roanan Ellis was unable to attended. Richard’s presentation gave a fascinating walkthrough of the process that is involved in getting the correct trim package. It started by looking at the sources of noise and transmission paths they will take for both internal and external noise, whilst comparing the diﬀ erence in frequency between traditional internal combustion engines, hybrid and electric vehicles. The presentation then progressed to the selection of the trim package and focused on airborne sound transmission paths due to time constraints. Richard discussed the methods of testing these materials, including absorption, transmission loss, damping, and the parameters of selection such as cost, weight and eﬀ ectiveness. The ﬁ nal part of the presentation covered how electric and autonomous vehicles will change the type of trim selected in the future, especially as driverless cars may need to reduce the focus of external noise and make the interior more comfortable. The Midlands Branch would like to thank Richard Crompton for a very well received and informative presentation.

On Wednesday, 24th March, IOA Southern Branch members met on Zoom for a presentation on the acoustic vehicle alerting system (AVAS) for London’s (TFL) emerging electric bus ﬂ eet. The presentation; ‘A soundscape approach to creating the urban bus sound’, was jointly presented by Anderson Acoustics’ Grant Waters and Ed Manzano, who set the scene by introducing TFL’s brief and vision for their new electric bus sound, and providing a concise technical overview of the current regulation governing sounds from electric vehicles at low speeds (< 20 kph): UN ECE Regulation 138. In short, their brief was to develop a balanced AVAS sound that was pleasant, safe and could improve urban soundscapes. Grant and Ed took attendees through the step-by-step evolution of the AVAS sound they created alongside their client and major stakeholders. They then described the early stages of their creative process, which involved a series of moodboarding workshops to generate a variety of potential sounds, and which eventually saw these whittled down to just 10 ﬁ nalists. They described how they reﬁ ned the characteristics of the sounds to ensure they remained pleasant to their collective ears, but also easily identiﬁ able and localisable by vulnerable road users and pedestrians – it was particularly interesting to learn how the requirements of the latter necessitated the addition of a comparatively impulsive ‘beacon’ sound, that would help people localise the source once the vehicle had begun to move. Following numerous computer simulations conducted in their SonicRoom and some ﬁ nal tweaks, they described how they were eventually ready to install the prototype onto a real bus and carry out in-situ tests. Grant and Ed ﬁ nished by informing us of the success of the prototype testing and successful approval of the system for trial on TFL’s Route 100. The presentation generated a lot of interest, with Zoom’s live chat becoming awash with questions and comments throughout the hour-long presentation. The level of engagement was a clear indication that this area of acoustics is still very much in its nascent form and the future will undoubtedly need to see synergy between the acoustics and automotive industries. The event was a great success, with 64 people in attendance. We hope to welcome Grant and Ed back following completion of phase two.

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64 ACOUSTICS BULLETIN MAY / JUNE 2021

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BRANCH NEWS

Scottish Branch

By Anne Budd

The Scottish Branch has had a busy start to 2021. Our postponed 2020 AGM was held 18 February when some long-standing members of the Branch decided it was time to step down and a new group of volunteers came forward to take on their roles. Many thanks to Alistair Somerville (IOA President Elect) for his many years as Chair of Scottish Branch and to Craig Simpson (Sandy Brown) for his time on the committee as Membership Secretary. Our new committee members are Lindsay McIntyre (KSG Acoustics), Chris Steel (HSE), Ashley Leiper (Envirocentre) and Mark Robertson (North Lanarkshire Council). Laurent Galbrun (Heriot Watt University), Nicola Symington (RMP), Martin Butterﬁ eld (Arup) and Lilianne Lauder (Mid Lothian Council) will continue in their roles on the committee. Anne Budd (New Acoustics) has taken on the role of Chair. We are also delighted to welcome Zanyar Abdalrahman (Sandy Brown) who has volunteered to be co-opted to the Scottish Branch Committee as Early Careers Group Representative. The new committee has an excellent mix of representatives from both commercial and public sectors and coverage from east and west of the country. We hope in future to encourage those members located further to the north and south of Scotland to join us, which is all much easier in these days of virtual meetings.

suggested that there are opportunities for consultants and researchers to get more involved as this novel area and the policy surrounding it develops. The presentation was well received and prompted a lengthy discussion and debate on many of the topics covered. The Scottish Branch, headed by Dick Bowdler and Anne Budd, has now taken on the role of coordinating an initial IOA Brieﬁ ng Note on the topic.

Edinburgh Science Careers Hive Event As well as our AGM the Scottish Branch have been busy preparing for the upcoming Edinburgh Science Careers Hive Event sponsored by the IOA. Normally a live event, as so many things have had to, this year the event will be entirely virtual on the Gather Town Platform. Students are invited to take part in a series of interactive events and workshops, allowing them to hear from inspirational early-career STEM professionals, speak directly with a variety of people working in the STEM industries and explore their own skills and strengths. IOA volunteers will man the virtual sound exhibition stand to talk about acoustics and careers with secondary school (S1-S3) students from across Scotland prior to them choosing the National Grade subjects. In addition, we are excited to see the IOA sponsored science experiment ‘Ella’s Wobble’ being sent out to primary schools in Scotland as part of the Edinburgh Science, Generation Science initiative, which despite having to be scaled back due to COVID constraints, is still going to be supporting the 200 most deprived primary schools in Scotland this year.

Noise control of drones The AGM was followed by an excellent presentation by Dick Bowdler (Dick Bowdler Acoustics) on the topic of ‘Noise from drones – are they the next environmental noise problem?’ Dick started his presentation by taking us through what is classed as a drone, which essentially are unmanned aerial vehicle or transportation systems. He then went on to tell us about the many types of drones which are already in use, including applications in photography and ﬁ lm, and those used for crop spraying. He outlined other potential uses, which are at various stages of design and development, even including examples of air taxi services. Dick noted that the main emerging use of drones is for delivery and gave examples of them in use and in trials across the world, including one in Scotland for delivery of medical supplies across from the mainland to islands oﬀ the west coast. He then took us through some of the research on noise from drones and the features which aﬀ ect it, such as the aerofoil trailing edge and noise from motors, as well as technical methods of mitigation. Dick described some of the factors relating to noise control of drones including the ethics of operational noise, parameters which could be used to best represent the noise and some existing and emerging regulation of drone noise. Finally, he

Branch plans and developments Our Scottish Branch programme of events for the year is taking shape and we hope to expand on what we have been oﬀ ering in recent years by taking on the lunchtime slot. To that end we are hoping to hear from Scottish Branch members about interesting projects they have been working on and on which they would be willing to present to the group, in a friendly lunchtime CPD session format. We are also planning to send out a short questionnaire to all Scottish Branch members on what more the IOA Scottish Branch can be doing in Scotland; for our members, but also to play a full role in the development of relevant legislation and national guidance, as well as inspiring our young people to take up careers in the ﬁ eld of acoustics and inﬂ uencing education and other areas of society. If have any questions do not hesitate to contact Anne Budd, Scottish Branch Chair, to discuss at anne@newacoustics.co.uk

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