An introduction by Jack Harvie Clark
The proposed revisions to BS 8233 - see the paper by Harvie-Clark and Fenech in the IOA Acoustics 2024 proceedings here and a webinar recording here - have sparked important discussions within our profession about how we can best protect public health through acoustic design. A letter published in the November/December 2024 issue of Acoustics Bulletin by Clarke and Fiumicelli access the letter here, signed by 33 experienced acousticians, raised important questions about our proposed approach to including external noise levels as key design criteria.
In response, Ben Fenech and I have prepared a detailed analysis access here exploring the scientific evidence that demonstrates the importance of the external sound environment in the noise and health relationship. Whilst our understanding of the quantitative relationship between noise exposure and health has improved significantly over the past two decades, the premise that both external and internal sound are important health determinants has not changed since the Environmental Health Criteria 12 were published by the WHO in 1980.
Building on strong foundations
The proposed revisions to BS 8233 seek to build upon our profession's strong track record in acoustic design. While our current practice of specifying internal sound levels equally for all sources has served us well in many ways, the evidence in the WHO 2018 Guidelines suggests we can enhance our approach to better protect public health.
Our proposals aim to integrate this evidence by recognising that different sound sources have varying health impacts at the same averaged sound level. The first significant suggestion in our proposals is that good environmental acoustic design is driven by the health evidence of adverse effects. This is a straight forward application of the evidence in the WHO 2018 guidelines, but it is in stark contrast to our current practice, where we treat all decibels equally.
The second significant suggestion in our proposals is that we should provide equivalent levels of sound insulation against sound that gives rise to equivalent adverse health impacts. This sounds simple, but implies different internal averaged sound levels for sound from road, rail and aircraft sources. This idea can be expressed either in terms of the same facade level difference, DnT,A,tr, as presented in our proposals, or it could be embodied by having different internal level targets for different sources. Both approaches achieve the same intent.
Understanding external and internal sound environments
Both these suggestions align with the evidence for adverse effects of transportation sound on people at home. One key discussion point raised in the Clarke and Fiumicelli letter concerns the relationship between external and internal sound levels. Our response demonstrates through multiple studies how both external and internal sound environments contribute to health outcomes. Rather than seeing external measurements as merely proxy indicators, the evidence shows they represent meaningful exposure metrics in their own right.
Studies from Öhrström and others reveal how people's experience of their home environment encompasses both indoor and outdoor spaces. Window-opening behaviour, use of outdoor areas, and overall environmental context all play crucial roles in determining health impacts. Our response details how these factors interact and why considering both external and internal sound environments is essential for effective acoustic design.
This new narrative squarely challenges a deeply held belief amongst many acoustic practitioners that if external sound levels are attenuated to suitable internal levels, effects on health are mitigated. The evidence clearly demonstrates that inside people’s homes, with sound that achieves the internal level guideline from WHO 1999 but with windows closed, the adverse health impacts are greater than where the internal level guidelines are met with windows open. The internal level guidelines from WHO 1999 were only ever supposed to be used together with the external level guidelines, not in isolation.
Considering the impact of external sound levels is not a new idea - it is already indicated in BS 8233 (2014) and the ProPG (2017). Our proposals take the approach of first considering the external levels and aligning the design drivers with the substantial evidence for different transportation sources.
The evolution of WHO guidelines
The relationship between the WHO's 1999 and 2018 Guidelines has been a topic of much discussion within our profession. In the January/February edition of the Acoustics Bulletin, readers will find an illuminating clarification from Dr Ben Fenech and Prof Stephen Stansfeld, Chair of the 2018 WHO Guidelines Development Group. Their article explains how the 2018 Guidelines represent a natural evolution in approach, building on previous work while incorporating new evidence.
This evolution reflects the WHO's move toward more rigorous, evidence-based methodologies. The 2018 Guidelines build on, rather than contradict, earlier work, helping us understand how internal and external sound environments work together to affect health outcomes.
A comprehensive framework
The proposed changes aim to create a more evidence-basedframework that recognises both external and internal acoustic environments. By considering facade sound insulation requirements in conjunction with external noise levels, we can better address the complex ways that environmental noise affects health and wellbeing.
This approach maintains our profession's commitment to controlling internal noise while incorporating new understanding about how different noise sources affect people in their homes. The framework provides flexibility to address various acoustic challenges while remaining grounded in evidence. We should not, however, tell ourselves that if we design to meet internal level targets with windows closed that we have mitigated all the adverse effects of the noise impact. We have done our best in those circumstances, but adverse effects remain.
Moving forward together
The consultation period for BS 8233 revisions offers our profession an opportunity to collaborate on enhancing our approach to acoustic design. We welcome all stakeholders to engage with the evidence and contribute their expertise to this important discussion.
We will be hosting further engagement events to facilitate detailed discussion of these proposals:
Scottish Branch Deeper dive into the proposals to update BS 8233 Thursday 9 January 2025 14:00 - 16:30 GMT Online only. https://www.ioa.org.uk/civicrm/event/info?reset=1&id=964
Proposals to update BS 8233 - a deeper dive Tuesday 14 January 2025 10:00 - 16:00 Voco Manchester, 59 Portland Street, M1 3HP In person only. https://www.ioa.org.uk/civicrm/event/info?reset=1&id=963
The consultation is currently intended to run from 24th December 2024 until the end of February 2025 (dates subject to change). Comments can be submitted at: https://standardsdevelopment.bsigroup.com/
Conclusion
As our understanding of noise impacts continues to evolve, so too must our approach to acoustic design. By working together to integrate new evidence while building on our profession's strong foundations, we can enhance how we protect public health through acoustic design. We encourage all colleagues to review both the original letter and our detailed response, and to come to your own conclusions. We look forward to hearing your views and response to this important discussion.
