The importance of head movements for localizing virtual auditory display objects

Abstract

In most of our research we produce virtual sound sources by filtering stimuli with head-related transfer functions (HRTF's) measured from discrete source positions and present the stimuli to listeners via headphones. With this synthesis procedure head movements create no change in the acoustical stimullus at the two ears, in contrast with what happens in natural listening conditions. To compare the localizability of virtual and real sources under these conditions, we require that listeners not m their heads, even when localizing real sources. Some listeners make large numbers of localization errors known as "front-back confusions" (a report of an apparent position in the front hemifield given a rear hemifield stimulus, and vice-versa). Head movements can, in theory, provide the cues needed to resolve front-back ambiguities. The experiment described here seeks to clarify the issue by meassuring both the nature and consequences of head movements during a sound localization task.