Cochlear Nonlinearities Implied by the Differences between Transient Onsets and Offsets to a Tone Burst
A trapezoidal tone burst (Figure 1) is equivalent to a sum of four ramp-modulated sinusoids. The response of any linearly operating spectral filter (or tuning structure) to a single ramp-modulated sinusoid is made up of two families of components: (a) for each natural frequency of the filter itself, a transient excitation equivalent to that which would have been produced by an impulse occurring precisely at the time of the onset corner of the ramp, and (b) with the same frequency as the stimulus, a step modulated sinusoid and a ramp modulated sinusoid, each beginning precisely at the time of the corner of the stimulus ramp. The amplitude of the transient excitation of each of the filter’s natural frequencies is directly proportional to the slope of the ramp and depends on the frequency of the stimulus relative to the natural frequency being excited (Lewis and Henry,’ 88). When the frequency of the stimulus sinusoid is close to or within the pass band of the filter, the transient excitations of the filter’s natural frequencies combine with the responses at the stimulus frequency to produce a “delayed” version of the input waveform. In that case, the transient excitations are manifested merely as the “delay” itself.
KeywordsCharacteristic Frequency Tone Burst Auditory Nerve Fiber High Stimulus Intensity Stimulus Sinusoid
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- Research supported in part by Grant 12359 from NINCDS, National Institutes of Health.Google Scholar