ASA 127th Meeting M.I.T. 1994 June 6-10

5pPP3. Reassessment of the role of head movements in human sound localization.

Frederic Wightman

Doris Kistler

Kristen Andersen

Dept. of Psychol. and Waisman Ctr., Univ. of Wisconsin, Madison, WI 53705

This project sought to quantify both the nature and consequences of a listener's head movements during a sound localization task. The task required listeners to report the apparent direction and distance of virtual sound sources. The virtual source stimuli were synthesized from measurements of each listener's own head-related transfer functions and were presented over headphones so that the acoustical consequences of head movements could be controlled. In one condition head movements were discouraged, and the stimuli delivered to the headphones were not influenced by movements of the listener's head. In another condition the listener was encouraged to use small head movements to aid localization. The position of the listener's head was tracked and the synthesis of each virtual source was modified in real time, in accordance with the head movements, to simulate a stationary external source. For those listeners who demonstrated a high rate of front--back confusions in the first condition, head movements apparently provided the information needed to resolve those confusions, since the confusion rate was near zero in the second condition. There was also some improvement in elevation perception with head movement information provided. Analyses of the head movement trajectories support the hypothesis that the major role of head movements is resolution of the confusions that result from reliance on interaural time and intensity cues. [Work supported by NIH, NASA, and the ONR.]