The Binaural Illusion of Wallach (1940) Apparent in Synthetic Aperture Images of the Field of Audition Generated as the Head Turns

Abstract

Wallach (J. Exp. Psychol. 1940, 27, 339–368) predicted that a human subject rotating about a vertical axis through the auditory centre, having an acoustic source rotating around the same axis at twice the rotation rate of the human subject, would perceive the acoustic source to be stationary. His prediction, which he confirmed by experiment, was made to test the hypothesis that humans integrate head movement information that is derived from the vestibular system and visual cues, with measurements of arrival time differences between the acoustic signals received at the ears, to determine directions to acoustic sources. The simulation experiments described here demonstrate that a synthetic aperture calculation performed as the head turns, to determine the direction to an acoustic source (Tamsett, Robotics 2017, 6, 10), is also subject to the Wallach illusion. This constitutes evidence that human audition deploys a synthetic aperture process in which a virtual image of the field of audition is populated as the head turns, and from which directions to acoustic sources are inferred. The process is akin to those in synthetic aperture sonar/radar technologies and to migration in seismic profiler image processing. It could be implemented in a binaural robot localizing acoustic sources from arrival time differences in emulation of an aspect of human audition.