Temporally diffusive reflections and the precedence effect

Abstract

In reverberant conditions, humans routinely demonstrate an ability to form the auditory event in the direction of the first wavefront and thus identify the direction of the (physical) sound source—the so-called “Precedence Effect.” Within limits, this effect even holds when the reflected sounds (the lag) contain more energy than the direct sound (the lead). Previously, we investigated the lateral extent of the Precedence Effect for specular reflections. The current research extends this inquiry by investigating the effect of temporally diffusive reflections, using the same stimuli, but convolving the lag with a 2-ms Hanning windowed Gaussian noise. The lead and lag stimuli were 200-ms Gaussian noise (500-Hz center frequency, 800-Hz bandwidth) presented dichotically with a programmable amount of temporal overlap. The lag/lead level ratio was increased in 2-dB steps, the lead/lag interval was varied from −5 to 5-ms in steps of 1-ms. Listeners indicated the lateralization of their auditory events with an acoustic pointer. The resulting temporal smearing substantially decorrelates lead and lag while keeping them essentially related. The Precedence Effect is found to be more robust to increases of the lag level for diffusive stimuli than for the previously tested sets of specular reflections.