Abstract
Amplitude modulation (AM) detection has been successfully used as a psychophysical measure of auditory temporal processing. Our understanding of the role of the auditory periphery in processing AM signals is emerging through physiological and psychophysical studies. Unfortunately, direct physiological estimates of the cochlea’s mechanical response to AM signals are not obtainable in humans. This study tries to fill this critical gap in knowledge by exploring the relationship between perception (through psychophysical AM detection) and mechanics (through otoacoustic emissions). Psychometric function for AM perception was measured for a 2-kHz carrier frequency and 10-Hz modulation frequency (fm). Distortion product otoacoustic emissions (DPOAEs) were recorded with amplitude-modulated f1 with fm = 10 Hz and steady-state f2. The frequencies of f1 and f2 were chosen to yield a 2f1 − f2 DPOAE around 2 kHz near a peak in the fine structure. The ratio between the DPOAE pressure at 2f1 − f2 and that of the sidebands separated by fm (AMOAE depth) was calculated as a function of different modulation depths. Results indicate that there might be a correlation between AM perception performance and AMOAE magnitude, suggesting that cochlear mechanics might play a role for AM perception. [Work supported by the Knowles Hearing Center and Northwestern University.]
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