Perceptual evaluation of listener envelopment using spatial granular synthesis

TL;DR

This study explores how the density and directionality of sound events affect listener envelopment and engulfment, using spatial granular synthesis to control these parameters and inform spatial sound design.

Contribution

It introduces a method to precisely control sound event density and directionality, revealing their effects on envelopment and engulfment in spatial sound perception.

Findings

Uniform sound distribution at intervals <20 ms induces diffuse envelopment.

Elevated loudspeaker layers enhance listener engulfment but not envelopment.

Lowpass filtering increases envelopment while reducing control over engulfment.

Abstract

Listener envelopment refers to the sensation of being surrounded by sound, either by multiple direct sound events or by a diffuse reverberant sound field. More recently, a specific attribute for the sensation of being covered by sound from elevated directions has been proposed by Sazdov et al. and was termed listener engulfment. This contribution investigates the effect of the temporal and directional density of sound events on listener envelopment and engulfment. A spatial granular synthesis technique is used to precisely control the temporal and directional density of sound events. Experimental results indicate that a directionally uniform distribution of sound events at time intervals $\Delta t < 20$ milliseconds is required to elicit a sensation of diffuse envelopment, whereas longer time intervals lead to localized auditory events. It shows that elevated loudspeaker layers do not increase envelopment, but contribute specifically to listener engulfment. Lowpass-filtered stimuli increase envelopment, but lead to a decreased control over engulfment. The results can be exploited in the technical design and creative application of spatial sound synthesis and reverberation algorithms.