A Precedence Effect in Sound Localization

The fact that sounds are localized in reverberant surroundings points up a critical problem which has not been explored sufficiently. A brief description will be given of experiments we have done which demonstrate that there is a precedence effect, whereby the first in line of a series of closely spaced sounds is the one which determines the place where the sound is heard. This demonstration of the importance of first arrival makes clear how we are able to discount the ambiguous clues from the reflected sounds of an ordinary hard-walled room. More extended measurements of the precedence effect have been made by synthesizing a sound out of four clicks arranged to give first one pair to the two ears representing one location, then a second pair to the ears representing a different location. Two parameters have been studied systematically, the interval between first pair and second pair, and the temporal disparity of the second pair. All measurements were made by varying the disparity of the first pair until the fused sound appeared to be in the middle of the head. Results of these experiments will be discussed.