Propagation of low frequency sound through an audience: a porous media and a radiative transfer approach Seminar

An audience typically covers a large area in front of the stage at an outdoor concert. In the past, the properties of audience as a “material” have been mainly studied in terms of absorption coefficients of seated audience in concert halls at mid- and high frequencies. Modern concert sound systems have a much lower frequency range and often utilise ground-stacked subwoofers that radiate straight into the audience. This makes understanding and correctly modelling the propagation of sound through an audience important both for concert sound system design and noise control.

This presentation shows ways to model a standing audience as a set of upright rigid cylinders with diameters and distances much smaller than the wavelength. A three-parameter porous media approach predicts the density-dependent speed of sound in the crowd quite well and agrees with both scale and live size experiments. This speed of sound is then used to predict modes and reflections within the audience.

Alternatively, one can model an audience using the radiative transfer equation, similar to forest acoustics. This approach uses the scattering amplitude of a person and predicts a rapid decrease of coherent intensity with distance.

Speaker External: Dr Elena Shabalina

Institution: d&b audiotechnik

Elena Shabalina received her degree in Physics, Fundamental Radiophysics and Physical Acoustics from the Lomonosov State University of Moscow, Russia, in 2008 and her PhD in Physics from the Institute of Technical Acoustics RWTH Aachen University in Germany in 2013. She joined the R&D department at d&b audiotechnik in 2012 where she is now responsible for Applied Research. Her research interests include wave phenomena, theoretical acoustics, outdoor sound propagation and noise control. Elena is the vice-chair of the AES Technical Committee on Acoustics and Sound Reinforcement and an international co-chair of the Internoise 2022 Conference. In 2022, she will join the Analysis and PDE Centre, Department of Mathematics of Ghent University as a guest researcher.

 

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