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 and binaural headphone auralizations, with and without real-time head tracking. The visuals were generated by a computer game engine and presented through a head-mounted display. Two differently sized rooms and an infinitely extending visual space (with simulated echoic and anechoic acoustics) were used containing an invisible frontal virtual sound source. Additionally, the effect of a freely movable virtual loudspeaker for visually indicating perceived distances was investigated. Both ADP and externalization were significantly affected by room size, but otherwise their outcomes differed: Room visibility significantly affected ADP, leading to considerable overestimations and more across-subject variability in the absence of a visual environment. The movable virtual loudspeaker improved distance estimation significantly. Conversely, externalization was significantly affected by reverberation and headphone rendering, with longer reverberation leading to improved externalization. A weak statistical connection between ADP and externalization was observed. While nearby sound sources are generally less externalized, distance can still be estimated largely independent of perceived externalization.