Combined assessment of auditory distance perception and externalization

This study investigates frontal auditory distance perception (ADP) and externalization in virtual audio-visual environments, considering effects of headphone rendering method, room size, reverberation, and visual representation of the room. Either head-related impulse responses from an artificial head or a spherical head model were used for diotic (monophonic) and binaural auralizations with and without real-time head tracking. The visuals were presented through a head-mounted display. Two differently sized rooms as well as an infinitely extending space (echoic and anechoic) were used in which an invisible frontal virtual sound source was located. Additionally, the effect of a freely movable loudspeaker for visually indicating perceived distances was investigated. Both ADP and externalization were significantly affected by room size, but otherwise the two perceptual quantities differed in their outcomes. Room visibility significantly affected ADP, leading to considerable overestimations and more variability in the absence of a visual environment, although externalization was not affected. The movable loudspeaker improved distance estimation significantly, however, did not affect externalization. For reverberation, a (non-significant) trend of improved ADP was observed, however, externalization was significantly improved. Different headphone renderings did not significantly affect ADP or externalization, although a clear trend was observed for externalization.

The effect of self-motion and room familiarity on sound source localization in virtual environments

This paper investigates the influence of lateral horizontal self-motion of participants during signal presentation on distance and azimuth perception for frontal sound sources in a rectangular room. Additionally, the effect of deviating room acoustics for a single sound presentation embedded in a sequence of presentations using a baseline room acoustics for familiarization is analyzed. For this purpose, two experiments were conducted using audiovisual virtual reality technology with dynamic head-tracking and real-time auralization over headphones combined with visual rendering of the room using a head-mounted display. Results show an improved distance perception accuracy when participants moved laterally during signal presentation instead of staying at a fixed position, with only head movements allowed. Adaptation to the room acoustics also improves distance perception accuracy. Azimuth perception seems to be independent of lateral movements during signal presentation and could even be negatively influenced by the familiarity of the used room acoustics.