A refined room acoustical simulation algorithm based on free path distribution

Abstract

Eyring’s or Sabine’s formula gives good results in rooms with a diffuse field. However, when long, flat, or coupled rooms, for example, are investigated, these formulas do not describe the decay correctly. The error has its reason in the assumption of an exponential decay with just one exponential coefficient calculated from the mean free path length and an averaged absorption coefficient. A new approach to calculate decay curves and reverberation time, already introduced by Vorländer [‘‘A fast room acoustical algorithm based on free path distribution’’ ICA 98] has been further refined. This method uses statistical results obtained by a short ray-tracing simulation. Free path length and absorption coefficient are statistically recorded for each reflection during this simulation. The recorded data represent the geometry of the room under investigation. In the next step several processes, each defined by an exponential function, are generated using this information, which are superposed to give a better approximation for the decay curve of the room. Some additional steps must be introduced to these processes to give reasonable results. This lecture will present the refined algorithm and some results.