Stimulus coherence influences sound-field localization and fusion/segregation of leading and lagging sounds.

The ability to localize sound sources in reverberant environments is dependent upon first-arriving information, an outcome commonly termed "the precedence effect." For example, in laboratory experiments, the combination of a leading (direct) sound followed by a lagging (reflected) sound is localized in the direction of the leading sound. This study was designed to measure the degree to which stimulus compactness/diffuseness (i.e., coherence as represented by interaural cross correlation) of leading and lagging sounds influences performance. The compactness/diffuseness of leading or lagging sounds was varied by either presenting a sound from a single loudspeaker or by presenting mutually uncorrelated versions of similar sounds from nine adjacent loudspeakers. In separate experiments, the listener's task was to point to the perceived location of leading and lagging 10-ms long low-pass filtered white noises or 2-s long tokens of speech. The leading and lagging stimuli were presented either from speakers located directly in front of the listeners or from speakers located ±45° to the right or left. The results indicate that leading compact (coherent) sounds influence perceived location more so than do leading diffuse (incoherent) sounds. This was true independent of whether the sounds were Gaussian noises or tokens of speech.