The Effect of Temporal and Directional Density on Listener Envelopment

Abstract

Listenerenvelopmentreferstothesensationofbeingsurroundedbysound,eitherbymultiple 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. The first experiment presented here investigates how the temporal and directional density of sound events affects listener envelopment. The second experiment studies how elevated loudspeaker layers affect envelopment versus 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 (cid:2) t < 20 ms 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. Low-pass-filtered stimuli enhance envelopment in directionally sparse conditions, but impede control over engulfment due to a reduction of height localization cues. The results can be exploited in the technical design and creative application of spatial sound synthesis and reverberation algorithms.