The contributions of onset and offset echo delays to auditory spatial perception in human listeners

Abstract

In echoic environments, direct sounds dominate perception even when followed by their reflections. As the delay between the direct (lead) source and the reflection (lag) increases, the reflection starts to become localizable. Although this phenomenon, which is part of the precedence effect, is typically studied with brief transients, leading and lagging sounds often overlap in time and are thus composed of three distinct segments: the "superposed" segment, when both sounds are present together, and the "lead-alone" and "lag-alone" segments, when leading and lagging sounds are present alone, respectively. Recently, it was shown that the barn owl (Tyto alba) localizes the lagging sound when the lag-alone segment, not the lead-alone segment, is lengthened. This was unexpected given the prevailing hypothesis that a leading sound may briefly desensitize the auditory system to sounds arriving later. The present study confirms this finding in humans under conditions that minimized the role of the superposed segment in the localization of either source. Just as lengthening the lag-alone segment caused the lagging sound to become more salient, lengthening the lead-alone segment caused the leading sound to become more salient. These results suggest that the neural representations of the lead and lag are independent of one another.

Effect of spectral overlap on the echo suppression threshold for single reflection conditions

“…Dizon and Colburn (2006) showed that precedence continues in the overlapping part of long duration stimuli. The influence of the lead-alone and the lag-alone parts of partially overlapping stimuli was examined by Donovan et al (2012). Since previous studies concerned with spectral differences between the lead and the lag were conducted without ensured buildup and with impulsive stimuli, the subsequently discussed comparisons of the present results to previous results have to be taken with caution and the underlying effects need further evaluation.…”

A Neural Model of Auditory Space Compatible with Human Perception under Simulated Echoic Conditions

“…The leading stimulus could have an ITD of -250 or +250 μs on any trial. However, locations indicated were analyzed as though the leading stimulus always came from the right (+250 μs ITD) and the lagging stimulus always came from the left (-250 μs ITD) [ 17 ].…”

“…Similarly, the lagging sound is present, alone, after the offset of the leading sound. These two segments, which are referred to as the “lead-alone” and “lag-alone” segments ( Fig 1A ), are analogous to the “glimpses” that listeners may occasionally be afforded in a typical auditory scene, during which spatial cues are relatively stable (i.e., coherent or correlated) [ 17 – 20 ]. In addition, a third segment is generated, when both stimuli are present, which is referred to as the “superposed” segment.…”

“…Even when both the leading and lagging sounds are perceived to be spatially distinct, the leading sound may dominate perception in that subjects report it as being more spatially salient than the lagging sound. The lagging sound’s location may also be perceived closer to the lead than its actual location [ 16 , 17 , 23 ]. Thus, localization dominance can persist beyond echo threshold and the location of the lagging sound, when heard as a spatially distinct event, may also be biased toward that of the lead.…”

Can monaural temporal masking explain the ongoing precedence effect?

“…With a pair of binaural pulses or noise bursts presented over headphones, for example, the interaural cues of the initial binaural transient contribute more to the lateral position of the composite intracranial image than the second transient (Wallach et al, 1949;Yost and Soderquist, 1984;ShinnCunningham et al, 1993). Other studies have demonstrated the precedence effect for ongoing sounds (Zurek, 1980;Braasch et al, 2003;Dizon and Colburn, 2006;Freyman et al, 2010;Donovan et al, 2012;Pastore and Braasch, 2015;Freyman and Zurek, 2017). Freyman et al (2010) explored the precedence effect for conditions with both abrupt and gradual gating and found only modest differences in the strength of the precedence effect.…”