ASA 124th Meeting New Orleans 1992 October

1aPP1. Precedence effect with and without interaural differences---Sound localization in three planes.

Brad Rakerd

Dept. of Audio and Speech Sci., Michigan State Univ., East Lansing, MI 48824

William Morris Hartmann

Michigan State Univ., East Lansing, MI 48824

Separate experiments measured the precedence effect for sound localization in the horizontal, frontal, and sagittal planes. The first two planes involve interaural differences, the third does not. Listeners (N=8) were required to localize trains of clicks, presented by loudspeakers in an anechoic room. A target click originating in a particular plane was followed by a simulated reflection of equal level from a different location within that plane. The delay between target and reflection was the principal independent variable; it varied from 0 to 10 ms. The results of the experiments showed that the precedence effect is more effective in eliminating localization confusion due to reflections when interaural differences are present. However, the functional dependence of target identification upon delay was similar whether interaural differences were present or not. For all three planes there were identical regions of summing localization, of increasing precedence effect, and of confusion caused by echoes. These results show that there is a sagittal plane precedence effect, and, therefore, that the precedence effect does not require interaural differences for its operation. [Work supported by the NIDCD, DC00181.]