Onset- and offset-specific effects in interaural level difference discrimination

Abstract

The relative sensitivity of human listeners to interaural level differences (ILDs) carried by the onsets, offsets, and interior portions of brief sounds was examined. Stimuli consisted of single 4000-Hz Gabor clicks (Gaussian-windowed tone bursts) or trains of 16 such clicks repeating at an interclick interval (ICI) of 2 or 5 ms. In separate conditions, ILDs favored the right ear by a constant amount for all clicks (condition RRRR) or a changing amount that was maximal at sound onset (condition R000), offset (condition 000R), both onset and offset (condition R00R), or at the temporal midpoint of the stimulus (condition 0RR0). ILD increases and decreases were implemented as linear decibel sweeps across four clicks to minimize transient distortion. Threshold ILDs were determined adaptively for each of these conditions and for single clicks. Thresholds were similar for ILDs presented near sound onset or offset (condition R000 vs 000R) but lower when ILDs were carried by both onset and offset clicks (condition R00R) than for ILDs carried by interior clicks alone (condition 0RR0). The results suggest that similar sensitivity to onset and offset ILD does not reflect uniform temporal weighting; instead, ILD sensitivity favors onsets and offsets over the interior portions of sounds.

Temporal dynamics and uncertainty in binaural hearing revealed by anticipatory eye movements

“…Blauert (1972) tested detection of changes in ILDs that were sinusoidally modulated, but limitations of that study were noted by Grantham (1984), who posited the distinction between perception of specific directional changes versus non-specific “differences.” Grantham showed that ILD changes become less perceptible as they are more rapidly alternating and also when they are carried by lower-frequency noises. The relative weakness of binaural change detection was also shown by Stecker and Brown (2012), who used a train of Gabor pulses to explore perception of binaural cues at multiple timepoints during a stimulus. They found that ILD sensitivity was poorer at the middle of the sound compared to the onset and offset.…”

Spectrotemporal weighting of binaural cues: Effects of a diotic interferer on discrimination of dynamic interaural differences

“…0R (p < 0.06). These results suggest that ILD cues are processed at both onset and offset (Stecker and Brown, 2012).…”

“…Regardless of the type of threshold calculation, significantly greater interference was observed in condition R0 than RR (p < 0.01) or 0R (p < 0.03), a result that runs counter to the hypothesis of reduced interference for cues at sound onset. Instead, the results suggest that late-arriving cues continue to play an important role in ILD discrimination (Stecker and Brown, 2012), even in the presence of an effective diotic interferer. BII did not differ significantly between condition 0R and RR (p < 0.4).…”

Temporal weighting of binaural information at low frequencies: Discrimination of dynamic interaural time and level differences

“…Our data for low-frequency pure tones appear consistent with at 1000 Hz, but with Stecker and Brown (2010) at lower frequencies (250 Hz). Stecker and Brown (2012) suggested that the discrepancies between these studies resulted from effects of onset and offset weighting in ILD processing (i.e., "U-shaped" temporal weighting functions, Stecker and Hafter, 2009). It is possible that similar issues pertain to the current data, although the stimuli and frequency range are quite different.…”

“…However, Stecker and Brown (2010) found no evidence for specific onset weighting in ILD, despite using stimuli (4000-Hz click trains) similar to those of . Results of that and a follow-up study which compared the weighting of ILD carried by onsets, offsets, and interior portions of sounds (Stecker and Brown, 2012) suggest that ILD cues near sound offset are strongly weighted, unlike the case for ITD, where the onset dominates more completely. Here, we investigate whether similar differences between ITD and ILD exist for low-frequency pure tones.…”