INCLUDING THE WALL SCATTERING COEFFICIENT IN THE DIFFUSION MODEL FOR BUILDING ACOUSTICS

摘要

For several years, an acoustic model has been developed to predict the reverberant soundfield in buildings. This model is based on the idea that the propagation of the reverberantsound field obeys a transport process and, for many cases, a diffusion process that canbe easily solved numerically. The work proposed here starts from the classical analyticaldevelopment achieved by Feshbach and Morse in 1953, showing that a transport equationcan be reduced to a diffusion equation. This model, valid in room acoustics for purelydiffuse reflections, is extended in the present study to mixed reflections (with a proportionof specular and diffuse reflections, i.e. considering a scattering coefficient). The proposedmathematical developments lead to an analytical expression of the diffusion constant thatis a function of the scattering coefficient, but also on the absorption coefficient of the walls.The results obtained with this modified diffusion model are then compared with the classicaldiffusion model, and with results obtained with a sound particle software, consideringmixed wall reflections.