Horizontal-plane localization of a target in the presence of a distractor: Effect of onset asynchrony

Abstract

Listeners localized a target in isolation and in the presence of a distractor. The target consisted of 10 10-ms Gaussian pulses (energy between 3–5kHz); the distractor was either a 100- or 500-ms narrowband (1–2 kHz) noise burst. The listener, with head unrestrained, was seated in the center of 36 loudspeakers spaced every 10 degrees on the horizontal plane and obscured by screens. On each trial, the target was played through a randomly selected loudspeaker. Listeners used a laser pointer to indicate target location. Pointer position was detected by infrared cameras and the response angle calculated. In separate conditions, distractor position was either fixed or randomized across trials, with target-to-distractor onset synchrony an additional parameter. The left-right component of responses was essentially unaffected by the presence of the distractor in any condition. With notable inter-subject variability, the front-back response component also showed little effect of the distractor. This absence of consistent effect of the distractor contrasts with previously reported work. The target and distractor in the present research, however, were generally more discriminable than in past studies, which likely mitigated at least some of the deleterious effect of the distractor on target localization ability.