Auditory distance perception in an acoustic pipe

In a study of auditory distance perception, we investigated the effects of exaggeration the acoustic cue of reverberation where the intensity of sound did not vary noticeably. The set of stimuli was obtained by moving a sound source inside a 10.2-m long pipe having a 0.3-m diameter. Twelve subjects were asked to listen to a speech sound while keeping their head inside the pipe and then to estimate the egocentric distance from the sound source using a magnitude production procedure. The procedure was repeated eighteen times using six different positions of the sound source. Results show that the point at which perceived distance equals physical distance is located approximately 3.5 m away from the listening point, with an average range of distance estimates of approximately 3.3 m, i.e., 1.65 to 4.9 m. The absence of intensity cues makes the acoustic pipe a potentially interesting modeling paradigm for the design of auditory interfaces in which distance is rendered independently of loudness. The proposed acoustic environment also confirms the known unreliability of certain distance cues.