The effect of an additional reflection in a precedence effect experiment

Abstract

Studies on the precedence effect typically utilize a two-source paradigm, which is not realistic relative to real world situations where multiple reflections exist. A step closer to multiple-reflection situations was studied using a three-source paradigm. Discrimination of interaural time differences (ITDs) was measured for one-, two-, and three-source stimuli, using clicks presented over headphones. The ITD was varied in either the first, second, or the third source. The inter-source intervals ranged from 0-130 ms. A perceptual weighting model was extended to incorporate the three-source stimuli and used to interpret the data. The effect of adding a third source could mostly, but not entirely, be understood by the interaction of effects observed in the precedence effect with two sources. Specifically, for delays between 1 and 8 ms, the ITD information of prior sources was typically weighted more heavily than subsequent sources. For delays greater than 8 ms, subsequent sources were typically weighted slightly more heavily than prior sources. However, there were specific conditions that showed a more complex interaction between the sources. These findings suggest that the two-source paradigm provides a strong basis for understanding how the auditory system processes reflections in spatial hearing tasks.

Lateralization of simulated sources and echoes differing in frequency based on interaural temporal differences

“…For longer echo delays, superior performance was obtained for judgments based on the echo, with the difference growing larger with increasing echo delay. Stellmack et al (1999), Litovsky and Shinn-Cunningham (2001), and Goupell et al (2012) have observed this same trend. All found superior performance based on the leading source at delays shorter than 10 ms and better performance based on the lagging echo at longer echo delays [out to 256 ms in Stellmack et al (1999)].…”

“…All found superior performance based on the leading source at delays shorter than 10 ms and better performance based on the lagging echo at longer echo delays [out to 256 ms in Stellmack et al (1999)]. Goupell et al (2012) extended this finding to three-pulse stimuli in which judgments were to be based on the first, second, or third. They reported best performance based on the first when the interval between the first and second pulse was less that 10 ms (as long as the lag between the second and third pulses was also less than 10 ms) and best performance based on the third when the interval between the second and third pulse exceeded 10 ms (regardless of the lag between the first and second pulse).…”

“…It appears that once one gets beyond echo delays that produce a precedence effect, performance is actually better when judging the echo pulse than the source pulse. This superior performance when judgments are based on information carried by last acoustic event has been termed a binaural "recency effect" Stecker and Hafter, 2009;Goupell et al, 2012).…”

“…Resolving the spatial location of the two intracranial images is not sufficient for performing the task. Perhaps listeners in Stellmack et al (1999) and Goupell et al (2012) formed separate intracranial images for the source and echo clicks when echo delays exceeded 8 ms but were confused as to which arose first. Indeed, Stellmack et al (1999) found that performance based on source pulses substantially improved when the ITD carried by the echo was fixed at 0 ls so that temporal order no longer needed to be resolved.…”

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

“…Correspondingly, leaddominance is viewed as having ended when the two sources were lateralized in equal proportions. Lag-dominance is defined as the preferential localization or lateralization of the lagging source (see also Litovsky and Godar, 2010;Goupell et al, 2012). The sources of lagging sounds are occasionally difficult to localize, a phenomenon referred to as lagdiscrimination suppression.…”