Free path statistics in coupled rooms

Abstract

Statistics of free paths in room acoustics led to the statistical reverberation theory of diffuse fields in spaces and thus to the well-known reverberation formulas. The specific distribution of free paths, however, can also give a more specific insight into the sound field and its deviations from the expected result using the mean free paths. Recently, Hanyu (JASA 128, 1140, 2010) extended the statistical reverberation theory toward a separation of absorption effects and mixing effects by scattering. This approach can predict nonlinear decay curves and the transition of energy between specular and scattered processes. In the work presented here, a concept of Vorländer (J. Sound Vib. 232, 129, 2000) is revisited. Free path distributions are logged in the room simulation program RAVEN and displayed in real time with regard to the geometric configuration of coupled spaces, and to the influence of absorption and scattering at the boundaries. This allows the observation of the decay curves in dependence on the actual free path distribution. From this data, it is tried to further develop simple prediction scheme of decay curves in non-diffuse and coupled spaces.