A fast room acoustical simulation algorithm based on the free path distribution

Abstract

A new algorithm is presented which provides estimates of impulse responses in arbitrary shaped rooms. It is applicable to any kind of room shape including nondiffuse spaces like workrooms or offices where, for instance, sound propagation curves are of interest. In the case of concert halls and opera houses it enables very fast predictions of room acoustical criteria like reverberation time, strength, or clarity. The algorithm is based on a conventional statistical ray tracing. However, a very low number of rays is used. During the ray tracing procedure, the distribution of free paths is recorded by considering the entire series of reflections per ray. Furthermore, the transition probabilities between free path classes and the absorption coefficients involved are stored. After the ray tracing, the free path distributions are evaluated by post-processing to create echograms. They include receiver-dependent direct sound and superposed exponential functions corresponding to classes of free paths. It is also possible to create reverberation tails without assuming a-priori diffuse sound fields and purely exponential decays.