Manipulations of listeners’ echo perception are reflected in event-related potentials

Abstract

To gain information from complex auditory scenes, it is necessary to determine which of the many loudness, pitch, and timbre changes originate from a single source. Grouping sound into sources based on spatial information is complicated by reverberant energy bouncing off multiple surfaces and reaching the ears from directions other than the source's location. The ability to localize sounds despite these echoes has been explored with the precedence effect: Identical sounds presented from two locations with a short stimulus onset asynchrony (e.g., 1-5 ms) are perceived as a single source with a location dominated by the lead sound. Importantly, echo thresholds, the shortest onset asynchrony at which a listener reports hearing the lag sound as a separate source about half of the time, can be manipulated by presenting sound pairs in contexts. Event-related brain potentials elicited by physically identical sounds in contexts that resulted in listeners reporting either one or two sources were compared. Sound pairs perceived as two sources elicited a larger anterior negativity 100-250 ms after onset, previously termed the object-related negativity, and a larger posterior positivity 250-500 ms. These results indicate that the models of room acoustics listeners form based on recent experience with the spatiotemporal properties of sound modulate perceptual as well as later higherlevel processing.

The effects of preceding lead-alone and lag-alone click trains on the buildup of echo suppression

“…First, the data suggest that buildup is reduced or "depressed" following a leadalone conditioner compared to an equivalent period of silence; this agrees well with previous observations (Sanders et al, 2011). Second, the data suggest that buildup is enhanced following a lag-alone conditioner compared to an equivalent period of silence.…”

“…Our findings join and complement a growing corpus of reports exploring the effects of lead-alone click trains on echo suppression (Freyman et al, 1991;Keen and Freyman, 2009;Sanders et al, 2011). First, data reported by Freyman et al (1991) demonstrated that echo thresholds of isolated lead-lag pairs decreased following a lead-alone conditioner, albeit in the absence of any explicit attempt to elicit buildup.…”

“…3 in Keen and Freyman (2009)]. Finally, Sanders et al (2011) demonstrated that buildup can also be reduced or "depressed" by a preceding lead-alone click train; the authors harnessed the depression in buildup to explore the neural correlates of echo suppression in human listeners. In every instance, a lead-alone click train reduces echo suppression and buildup, regardless of whether the lead-alone click train precedes or follows buildup.…”

“…In other words, the lag sound of lead-lag pairs becomes more perceptually salient or "surprising" when it has been recently absent from the listening environment. A recent investigation into the effects of a lead-alone click train prior to establishing buildup-that is, when a lead-alone click train is presented before buildup-has provided additional support for the importance of "contrast" in echo suppression (Sanders et al, 2011). Specifically, Sanders et al (2011) demonstrated that buildup is less robust or "depressed" when a lead-lag click train is presented after a lead-alone click train; this suggests that lag clicks may be more perceptually salient or more "surprising" following a lead-alone click train than with buildup alone.…”

“…A recent investigation into the effects of a lead-alone click train prior to establishing buildup-that is, when a lead-alone click train is presented before buildup-has provided additional support for the importance of "contrast" in echo suppression (Sanders et al, 2011). Specifically, Sanders et al (2011) demonstrated that buildup is less robust or "depressed" when a lead-lag click train is presented after a lead-alone click train; this suggests that lag clicks may be more perceptually salient or more "surprising" following a lead-alone click train than with buildup alone. Together, these reports suggest that a lead-alone click train can have a powerful effect on buildup in two ways: (1) a lead-alone click train can breakdown established buildup and (2) buildup becomes less robust following a lead-alone click train, likely due to the high contrast between lead-alone clicks and lead-lag click pairs.…”