THE INFLUENCE OF BROAD-BAND NOISE ON THE PRECEDENCE EFFECT

This study examined the influence of background noise on the localizat ion of lead-lag noise-burst pairs and on echo threshold for the same s timuli. Experiments were conducted in an anechoic chamber with a leadi ng stimulus delivered from a loudspeaker at 45 degrees to the right of center and a lagging stimulus from 45 degrees left. Lead and lag stim uli were 4-ms bursts of Gaussian noise. In experiment 1, with lead and lag at equal levels and the lag delay fixed at 2 ms, the perceived lo cation of the image produced by the lead-lag stimulus was estimated fr om subjects' left/right judgments relative to bursts from a ''comparit or'' loudspeaker whose position could be adjusted. In experiment 2, th e dominance of the leading burst on perceived location was measured by determining the increase in level of the lagging burst necessary to p roduce an image estimated to be centered at 0 degrees azimuth. Experim ent 3 was concerned with echo threshold. Subjects reported whether or not they heard a sound in the vicinity of the lagging loudspeaker as t he lag-burst delay was varied. In all three experiments, data were obt ained for four to five stimulus levels in quiet and for three levels o f background white noise from a loudspeaker at 180 degrees. The result s revealed a substantial weakening effect of background noise on the p recedence effect in experiments 2 and 3, and a nonsignificant effect i n experiment 1. (C) 1998 Acoustical Society of America. [S0001-4966(98 )03310-4].