M. A. Stellmack
E. A. Macpherson
Waisman Ctr., Univ. of Wisconsin-Madison, 1500 Highland Ave., Madison, WI 53705
Localization of a virtual acoustic source in isolation was compared to that for the same source played in the presence of a distractor source. The target stimulus was a tonal complex consisting of a 253-Hz fundamental and all harmonics below 14 kHz. The distractor stimulus was a similar tonal complex with a 353-Hz fundamental. Both target and distractor were 250 ms in duration. Virtual sources were generated by filtering the source stimuli with individualized head-related transfer functions (HRTF's), and the resulting stimuli were presented over headphones. Listeners were instructed to place an acoustic pointer (wideband noise source) at the same apparent position as the target by pressing buttons on a response terminal to manipulate the pointer position. Listeners were allowed to play the test stimulus and pointer at will during each trial. The variability of the pointer responses was similar in the two conditions (target alone and target-plus-distractor), but the difference between the actual target position and the average pointer position was larger when a distractor was present. Responses in the target-plus-distractor conditions tended to be biased toward the distractor position, particularly when the target and distractor were on the same side of the head.