Coherence-based diffuseness estimation in the spherical harmonic domain

The diffuseness of sound fields has previously been estimated in the spatial domain using the spatial coherence between a pair of microphones (omnidirectional or first-order). In this paper, we propose a diffuseness estimator for spherical microphone arrays based on the coherence between eigenbeams, which result from a spherical harmonic decomposition of the sound field. The weighted averaging of the diffuseness estimates over all eigenbeam pairs is shown to significantly reduce the variance of the estimates, particularly in fields with low diffuseness.