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

2pPP56. Localization suppression and echo suppression aspects of the precedence effect.

Xuefeng Yang

D. Wesley Grantham

Bill Wilkerson Ctr. and Div. of Hear. and Speech Sci., Vanderbilt Univ. School of Medicine, 1114 19th Ave. South, Nashville, TN 37212

The precedence effect is a phenomenon that may occur when a sound from one direction (the lead) is followed within a few milliseconds by the same or a similar sound from another direction (the lag, or the echo). Typically the lag sound is not heard as a separate event and the lag sound cannot be localized. Traditionally these two aspects of precedence (echo suppression and localization suppression) have been assumed to represent the operation of a single mechanism. The hypothesis is proposed in this study that localization suppression and echo suppression are at least partially independent phenomena. A series of experiments was conducted to test this hypothesis as well as to investigate the acoustic parameters that affect the magnitude of localization suppression and echo suppression. In the first experiment subjects showed a significantly greater degree of echo suppression than of localization suppression when presented with an extended train of lead-lag noise burst pairs. In other experiments it was shown that the magnitude of localization suppression is affected primarily by the degree of spectral overlap of lead and lag sounds, and to a lesser extent by the relative ``localization strength'' of the two sounds [P. L. Divenyi, 1078--1084 (1992)]. [Work supported by NIDCD.]