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.]