Can basilar membrane tuning be inferred from distortion measurement?
As the frequency of two tones progressively converge, an increasing number of distortion sidebands of the family (n+1)f1-nf2 (where n is a positive integer) can be detected in cochlear electrical and mechanical responses. If the distortion is measured in the ear canal sound pressure when the stimulus levels are low, each distortion component follows a simple pattern of a rise to a maximum in magnitUde, followed by a decline, often to the noise floor, as the fl and f2 frequencies approximate (Wilson, 1980; Brown & Kemp, 1985; Harriset al.,1988). Distortion has its origin at the stimulus frequency place for the higher frequency stimulus (f2) in the cochlea (Hall, 1980; Kim et al.,1980), so it is somewhat surprising that distortion level decreases as its own frequency approaches that of 1’2. The aim of this work was to see whether the distortion-generating mechanism itself is being suppressed as the stimuli are approximated in frequency or whether the distortion is being subjected to some secondary filtering.
KeywordsStimulus Level Tectorial Membrane Distortion Level Distortion Component High Frequency Stimulus
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