REPRODUCED SOUND 2020

Throughout this paper, the term ‘Sound Systems for Emergency Purposes’, SSEP, will be used to include ‘Emergency Communications System’, ECS, as defined in NFPA72:2016 and ‘Voice Alarm Systems’, VAS, as defined in BS EN54-32:2015 and BS 5839-8:2013. The SSEP industry constantly evolves due to the implementation of newer technologies. The motivation behind these developments are often attributed to emerging “green” requirements to be energy efficient and space saving to provide physically smaller systems thereby freeing up precious real estate.

The most current guidance document used in the UK for the control of music noise at events is the ‘Noise Council, code of practice on environmental noise control at concerts, 1995’ (referred to going forward as the ‘Pop Code’). The published levels from the Noise Council are presented in Table 1 below. Table 1 - Summary of the suggested limits presented in the Pop Code Research undertaken in 2006 (Griffiths & Staunton, 2006) suggested that the guidance would benefit from further refinements to the noise levels, the number of concerts and the categories used.

Qingdao Movie Metropolis Grand Theatre (the Grand Theatre) is located within the 400-acre Qingdao Movie Metropolis in Qingdao, the world’s largest movie and television production hub. The Grand Theatre was purposely designed as the main venue for the proposed Qingdao International Film Festival. It is the largest movie theatre in Asia, and the only theatre in the world installed with both Dolby Atmos, and an electronic room enhancement system. The total floor area is 24,000 m2 . The auditorium seats an audience of 1970, including 1298 seats in the stalls and 672 seats in a single balcony.

Coherence is reduced by uncorrelated noise, distortion, and reflections which occur outside the analysis window. A procedure has been proposed for measuring the Max Linear SPL of loudspeakers which has both a frequency response compression criterion and a coherence reduction criterion. The purpose of the coherence criterion is to detect the onset of distortion anywhere in the system under test. It is usually possible to find an acoustic environment whose background noise is low enough to start with high coherence.

Acoustic Directions (AD) has developed a low-cost acoustic flow resistance meter to determine the specific airflow resistance and resistivity of fabrics, textiles and insulation. Acoustic flow resistance can be expressed in three forms: a) The airflow resistance is defined as the ratio of the pressure difference across a sample to the volume velocity of flow of air through the test sample, and is measured in mks acoustic ohms (Pa·s/m3 ).

The development of computational power in recent years has enabled the use of large training datasets in machine learning. Training neural networks can still be very time consuming and this has led to the development of computationally efficient neural network implementations such as TensorFlow1 , PyTorch 2 , Keras and Scikit-Learn3 or the MATLAB Deep Learning Toolbox4 .

Current methods of determining acoustical parameters must adhere to current standards, require necessary training, include high equipment costs, and is time-consuming. The estimation of acoustics through calculation diminishes some issues with acoustics measurement but can be less accurate1 . It can be difficult for individuals and businesses in the acoustics field to consider RT60 despite its importance as an influential acoustic parameter2 which arguably cannot be assumed, especially within educational spaces3,4 .

When sound system designers are selecting loudspeakers and amplifiers to produce a given sound pressure level, parameters that must be determined are the required power capacity of amplifiers, and the sensitivity and power handling capacity of the loudspeakers. Integral to the determination of these parameters is a knowledge of the long-term Leq (or RMS level) and the crest factor of the programme material that is to be fed to the system for broadband and specific frequency bands.

Finite and boundary element simulation techniques1 are now commonly used in designing audio systems. There may be many components involved, e.g. a compression driver, a transition section changing cross section from circular to rectangular at the throat of the horn, a cylindrical waveguide terminating in a baffle. A model can be used to analyse the entire system. Ideally the wavefronts should be well behaved throughout, as sound progresses through the system.