The role of envelope waveform in the processing of high- frequency interaural timing disparities
Abstract
Interaural timing disparities provide an important cue for lateralization in the human auditory system. The auditory system is sensitive to timing disparities in the ne-structure and the envelope of sounds. In the normal-hearing system, only envelope disparities can be exploited at high frequencies due to the lack of phase-locking to the ne-structure. Similarly, in cochlea implant users, interaural timing disparities of the envelope are of importance. It is, however, still unclear which speci c envelope waveform properties promote the most stable features for lateralization. In this study, psychophysical measurements were conducted with customized envelope waveforms in order to investigate the isolated effect of attack and decay times, as well as pause and hold durations in the envelope waveform on lateralization. For high-frequency tones centred at 4 kHz with systematic envelope modi cations, the just noticeable differences of ongoing interaural time differences in the envelope were measured. The results indicate that attack times and pause durations prior to the attack are the most important envelope features. The results are compared to predictions of binaural auditory models with different adaptation mechanisms prior to their binaural stage. Consequences of the different adaptation mechanism for monaural processing and for processing of cochlea-implant-like stimulation are discussed.
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