Minimum audible angle at the subjective front during listener’s head rotation

Abstract

Sound localization is a multisensory process consisting not only of hearing, but also of self-motion perception. A large number of studies have shown that the listener’s head movement, particularly horizontal rotation, effectively improves sound localization acuity (Wallach, 1939; Thurlow, 1967; Kawaura, 1989; etc.). However, research into sound localization during head rotation is scarce. Thus, the multisensory process underlying sound localization remains unclear. In the present study, we directly investigated the minimum audible angle (MAA) — the detection threshold needed for the listener to localize sounds at different positions — at the front during horizontal head rotation. A sound stimulus (30-ms noise burst) was presented from a loudspeaker of a circular array (r = 1.1 m), with a loudspeaker separation of 2.5 degrees. The listener, sitting at the center of the circle, was asked to answer whether the sound stimulus was presented from the left or right of the subjective front (2AFC). We considered two listening conditions, static and dynamic. In the static condition, listeners were asked to keep their heads still. Meanwhile, for the dynamic condition, listeners were asked to rapidly rotate their heads; the test stimulus was triggered during head movement. Sound stimuli were presented from a randomly selected loudspeaker out of a subset of 13 centered at the listener’s physical front at the time of stimulus presentation. Results showed the MAA to deteriorate significantly in the dynamic condition. This implies that the improvements in sound localization due to head motion could be explained by the multiple-look model (Viemeister and Wakefield, 1991).