Binaural perception of direct and reverberant sound fields rendered with mixed-order spherical harmonics

Abstract

Binaural responses can be rendered from a plane-wave decomposition of a measured or a modeled sound field, spatially integrated with free-field head-related transfer functions. When represented in the spherical-harmonics domain, the decomposition order reflects the maximum spatial resolution, which is limited by the number of microphones in the spherical array. Recent studies suggest a direct relationship between decomposition order and perceptual attributes such as localization blur, timbre, and the sense of externalization. Insofar, studies have employed plane wave density functions in which the different components of the sound field were uniformly decomposed at a single spherical-harmonics order. This work is concerned with binaural signals in which the direct and reverberant parts of the sound field are decomposed at different spherical-harmonics orders. The direct component of the sound field carries significant directional information utilized by the auditory system. Therefore, changing the spherical-harmonics order of the direct component is expected to have a different perceptual impact compared to changing the spherical-harmonics order of the reverberant part. Listening experiments are employed to study the perception of such mixed-order representations in context of sound localization and auditory distance perception.