Hearing silent shapes: Identifying the shape of a sound occluding surface

While most psychoacoustics is concerned with perception of sound sources, there is evidence that surfaces which reflect or occlude sound can also be detected and can guide behavior [e.g., M. S. Gordon and L. D. Rosenblum, J. Acoust. Soc. Am. 107, 2851 (2000)]. While there is also evidence that listeners can hear the shape of sound reflecting surfaces [e.g., C. E. Rice, Science 155, 655–664 (1967)], it is not known whether the shape of sound occluding surfaces can be heard. In a series of experiments, blindfolded listeners were asked to judge the shape of surfaces (of equal area) which occluded a set of loudspeakers emitting white noise. Overall, listeners were successful at this task, with some listeners showing near perfect performance. Follow-up experiments examined the acoustic information supportive of this skill. The findings suggest a type of auditory sensitivity not often considered in the psychoacoustics literature.