ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP57. The effect of background noise on the precedence effect.

Yuan-Chuan Chiang

Richard L. Freyman

Dept. of Commun. Disorders, 6 Arnold House, Univ. of Massachusetts, Amherst, MA 01003

The current experiment examined the influence of noise on the precedence effect, focusing on the importance of noise source location. Listeners seated in an anechoic chamber judged whether the image produced by a lead-lag pair of 4-ms noise bursts (2-ms delay) was to the left or right of midline. The lag loudspeaker was fixed at 45(degrees) to the left or right, while the lead loudspeaker was positioned at a variable number of degrees to the opposite side. The angle of the lead loudspeaker producing 50% judgements favoring the lead was used to estimate its perceptual weighting relative to the lag. This weighting, which was quantified using the c metric developed by Shinn-Cunningham et al. [ 2923--2932 (1993)], strongly favored the lead when the sounds were presented in quiet. The value of c was reduced markedly when background broadband noise was introduced from 0(degrees) or 180(degrees) angles, supporting previous findings of a weakened precedence effect in noise. When the background noise source was off-midline, or lead-lag pairs of noise sources were used, the effects of noise on c were complex and asymmetric. [Work supported by NIH #DC01625.]