Analysis of multi-exponential and anisotropic sound energy decay

The sound field in coupled rooms or rooms with non-uniform absorptive material distributions can be considerably anisotropic. In such scenarios, the sound energy decays with more than one decay rate, thus making it practical to use a decay model that consists of multiple exponential decays and a noise term. In this work, we use a recently proposed neural-network-based approach for estimating the underlying model parameters from sound energy decay curves. Introducing a spherical filter bank allows for a directionally constrained analysis of anisotropic late reverberation, resulting in a set of multi-exponential decays with corresponding decay parameters. Additionally, the paper introduces the common-slope model of directional reverberation, in which directional or spatial decay variations are described in terms of exponential amplitudes while fixing the corresponding decay times. Our work shows that the proposed analysis framework is suitable for modelling anisotropic sound fields with multi-exponential decays and that it can be used for challenging acoustic problems, such as the denoising of spatial room impulse responses.