Sound localization with a preceding distractor.

Experiments explored how a distractor coming from a known location influences the localization of a subsequent sound, both in a classroom and in an anechoic chamber. Listeners localized a target click preceded by a distractor click coming from a location fixed throughout a run of trials (either frontal or lateral). The stimulus onset asynchrony (SOA) between distractor and target was relatively long (25-400 ms); control trials presented the target alone. The distractor induced bias and variability in target localization responses even at the longest SOA, with the specific pattern of effects differing between the two rooms. Furthermore, the presence of the distractor caused target responses to be displaced away from the distractor location in that run, even on trials with no distractor. This contextual bias built up anew in each run, over the course of minutes. The different effects illustrate that (a) sound localization is a dynamic process that depends on both the context and on the level of reverberation in the environment, and (b) interactions between sequential sound sources occur on time scales from hundreds of milliseconds to as long as minutes.