Propagation and reverberant phase in acoustical spaces

Abstract

Systems with low modal overlap cannot support a “direct field” and have also been shown to have a phase trend and corresponding group delay that is far in excess of the expected propagation delay. The phase trend that is associated with this behavior has been termed “reverberant phase.” The reverberant phase also shows up in systems with high modal overlap, but in such systems, the phase of the direct (or propagation) field is expected to also be present. If the effects of reverberation could somehow be subtracted from the data, one would expect to see the propagation phase. In this paper, a procedure for the decomposition of propagation and reverberant phase components from a received signal is presented, using properties of the complex cepstrum. These ideas are tested experimentally using data from transfer functions for small acoustical chambers. Directions for future work on this topic will also be discussed. [Work supported by NTT Research and Development Center.]