Evidence for an across-frequency, between-channel process in asymptotic monaural temporal gap detection

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Signal Processing in Hearing

Background:

• Temporal gap detection (TGD) thresholds typically increase with frequency separation between gap-marking sinusoids.
• This pattern suggests both within-channel and between-channel auditory processing.
• The precise mechanism for asymptotic TGD at large frequency separations remains unclear.

Purpose of the Study:

• To test the hypothesis that asymptotic monaural gap detection involves between-channel processing.
• To investigate TGD thresholds using dichotic presentation of gap-marking sinusoids across different frequencies.

Main Methods:

• Measured TGD thresholds with a pregap sinusoid in the left ear and a postgap sinusoid in the right ear.
• Varied the frequency separation between the left and right ear sinusoids across a range of 250 Hz to 4000 Hz.
• Compared dichotic TGD thresholds with previously measured asymptotic monaural TGD thresholds.

Main Results:

• Dichotic TGD thresholds remained relatively invariant, showing only slight increases with wider frequency separations.
• Average TGD thresholds ranged from 30 to 40 ms for four listeners.
• These dichotic results closely matched the asymptotic monaural TGD thresholds under similar conditions.

Conclusions:

• The findings support an across-frequency, between-channel processing mechanism for asymptotic monaural gap detection.
• This processing likely occurs centrally, integrating auditory information from independent frequency channels.
• The study elucidates the neural basis of temporal gap detection in complex auditory scenes.