| 1997, 613, Session T6, Poster |
| "Missing fundamental" and inner hair cell "filtering" |
| *Y. Cai, E.J. Walsh, J. McGee (Boys Town National Research Hospital, Omaha, NE) |
| It is commonly known that the physical presence of the fundamental component of a harmonic complex is not required to generate the fundamental pitch of a complex signal (i.e., the phenomenon of the "missing fundamental"). We propose a corollary of that phenomenon in which the physical presence of the fundamental component is not important from a perceptual perspective. We postulate that regardless of whether or not the fundamental frequency is a component of a given stimulus, the fundamental frequency of such acoustic events is typically "missing" from cochlear output as a consequence of the hydraulic, highpass filtering that occurs at the inner hair cell (IHC) stage of transduction. This idea was tested in a computer model, consisting of a first-order highpass filter with a corner frequency of 500 Hz, a rectifying IHC transfer function, and a first-order lowpass membrane filter with a corner requency of 1200 Hz (cf. Cai and Geisler, Hear. Res. 96, 126- 140, 1996). Simulation results indicate that the output of IHCs (and thus activity in auditory-nerve fibers) is unaffected by the presence of the fundamental component of a low to moderate level harmonic complex. This outcome supports the hypothesis that the fundamental component is attenuated within the cochlea; i.e., the fundamental component is attenuated in the responses of auditory-nerve fibers with characteristic frequencies at both the fundamental and harmonic frequencies. Thus, when the fundamental frequency is low, the central auditory system must rely on periodicity information carried in the harmonic structure of the acoustic signal and provided mainly via auditory-nerve fibers with characteristic frequencies of the harmonics to make pitch judgments. |
| Supported by NIDCD DC01007. Yidao Cai is supported (in part) by NIDCD P60 DC00982-06
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Citation for this abstract:
Cai, Y. E.J. Walsh, and J. McGee (1997). "Missing fundamentals and Inner hair cell filtering". Assoc. Res. Otolaryngol. Abstr., p.154.
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