Spatial resolution of late reverberation in virtual acoustic environments

TL;DR

This study investigates how reducing the spatial resolution of late reverberation in virtual environments affects perceptual accuracy, finding that 12 to 24 sources are needed for realistic sound field simulation.

Contribution

It identifies the minimum number of virtual reverberation sources needed to perceptually and technically approximate high-resolution diffuse sound fields in virtual acoustics.

Findings

12 to 24 reverberation sources are required for perceptual approximation.

Reducing spatial resolution affects the coherence of the sound field.

Number of sources influences the realism of virtual acoustic environments.

Abstract

Late reverberation involves the superposition of many sound reflections resulting in a diffuse sound field. Since the spatially resolved perception of individual diffuse reflections is impossible, simplifications can potentially be made for modelling late reverberation in room acoustics simulations with reduced spatial resolution. Such simplifications are desired for interactive, real-time virtual acoustic environments with applications in hearing research and for the evaluation of hearing supportive devices. In this context, the number and spatial arrangement of loudspeakers used for playback additionally affect spatial resolution. The current study assessed the minimum number of spatially evenly distributed virtual late reverberation sources required to perceptually approximate spatially highly resolved isotropic and anisotropic late reverberation and to technically approximate a spherically isotropic diffuse sound field. The spatial resolution of the rendering was systematically reduced by using subsets of the loudspeakers of an 86-channel spherical loudspeaker array in an anechoic chamber. It was tested whether listeners can distinguish lower spatial resolutions for the rendering of late reverberation from the highest achievable spatial resolution in different simulated rooms. Rendering of early reflections was kept fixed. The coherence of the sound field across a pair of microphones at ear and behind-the-ear hearing device distance was assessed to separate the effects of number of virtual sources and loudspeaker array geometry. Results show that between 12 and 24 reverberation sources are required.