ASA 127th Meeting M.I.T. 1994 June 6-10

3pPP14. More on the precedence effect in three planes.

Brad Rakerd

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

William Morris Hartmann

Michigan State Univ., East Lansing, MI 48824

Following previous experiments [Rakerd and Hartmann, J Acoust. Soc. Am. 92, 2296 (A) (1992)] the precedence effect was studied in azimuthal, frontal, and sagittal planes. The first two planes involve binaural differences, the third plane does not. Experiment I required the listener to localize a target click, presented in an anechoic room, in competition with a lagging click, presented from a different location in the plane under study. The lagging click followed the target by a delay of 0.5, 1, 2, or 5 ms. For each plane, the experiment tracked the decrease in precedence effect as the level of the lagging click became greater than the level of the target (0--12 dB). The results showed similar dependencies in all three planes, indicating a universality of precedence effect. Experiment II required the listener to report perceived echoes, thus determining echo threshold, as a function of the same delay and level-difference variables. The results showed higher echo thresholds in the sagittal plane compared with the other two. Both experiments indicate significant precedence effect in the absence of binaural differences. [Work supported by the NIDCD, DC00181.]