Abstract:

Listeners gave verbal apparent position estimates in response to a frozen 250 ms wideband noise burst presented from one of 36 locations in virtual free-field. A click train and a modulated harmonic complex, both presented simultaneously with the noise target, served as distracters. On each trial, the distracters were presented in one of six randomly chosen configurations in virtual space. All virtual sources were synthesized from the listeners' own HRTFs. The impact of the distracters on the apparent position of the target varied considerably across listeners. For all listeners, when the distracters were presented on the horizontal plane at +90 degrees and -90 degrees (directly opposite the two ears), the apparent elevation and front-back position of the target were disrupted. For some listeners, this was the only effect of the distracters. In a separate condition, the stimuli were presented ten times in succession and listeners were encouraged to move their heads during stimulus presentation. Synthesis of the virtual sources was coupled to head position in order to simulate stationary virtual sources. In this condition the distracters had no effect on the apparent position of the target. [Work supported by ONR.]