Changes in head position as a measure of auditory localization performance: auditory psychomotor coordination under monaural and binaural listening conditions.

Two experiments examined the capacity of listeners to turn and face an active sound source. Tests were conducted with sources located in the subject's forward field (an arc extending from 60 degrees to the subject's right to 60 degrees to the left). Localization performance was determined under both monaural and binaural listening conditions, using both brief pulses and sustained pulse trains as target signals. Not unexpectedly, the ability to orient the face to a hidden sound source was very poor under monaural conditions if the listener received only a brief (100-ms) tonal pulse. When continuous pulse trains were employed, localization, even under monaural conditions, became quite accurate. Across conditions, this complex motor response produced results in agreement with those that have been obtained when subjects were only required to report their spatial impressions. In particular, performance with binaural pulse trains was observed to vary as a function of the frequency of the target signals employed. Descriptions of the head movement response, along with a discussion of some of the implications of ear-head coordination, are presented.