My 50 years of cochlear modeling

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The goal of this presentation is two-fold: The primary goal is to discuss my present understanding of cochlear function. A secondary goal is to review my earlier (1970-2021) cochlear modeling work, along with the roles of four close friends: Egbert De Boer, Steve Neely, Paul Fahey and George Zweig. To understanding of how the cochlea works, one needs an understanding of the experimental data on: 1) cochlear function (both basilar (BM) and tectorial membranes (TM)), 2) tympanic membrane, 3) middle ear (ME), 4) inner and outer hair cells (IHC, OHC), 5) auditory nerve (AN), and 6) cochlear amplifier (CA). My views on these topics have been greatly sharpened by looking back and unifying this complex puzzle. A great deal of progress has been made in the last 50 years. Conclusions: My recent review of neural tuning curve data from 1985, using nonlinear (NL) distortion product generation, has revealed a deeper understanding of cochlear function. The most important, and surprising result, is that the cochlea is much more linear in its filtering properties than I previously assumed. When the suppressor frequency fs is at least 1/2 octave lower than the characteristic (“best”) frequency (fcf ), it is best known as “low-side” suppression. There is no “low-side” suppression for suppressors below 65 [dB-SPL] Fahey and Allen [1]. For suppressors above 65 [dB-SPL], suppression is engaged, with a slope between 1-2 [dB/dB]. Since the excitation threshold is also 65 [dB-SPL], we conclude that the neural threshold of excitation to both the inner and outer hair cells have nearly the same threshold. That is the suppression threshold of the OHC are nearly equal to, the IHC threshold. This raises the interesting question: If the IHC and OHC 65 [dB] thresholds are the same in the tails of the tuning curves, how can the CA function at threshold levels? Furthermore this is a highly unexpected result because low-side suppression, as measured on the basilar membrane, has a 20-30 [dB] higher threshold [2, 3]. Is the OHC action restricted to the neighborhood of the neuron’s best frequency? This would require that the neural low-side suppression and loudness recruitment (the reduced loudness of low-intensity sounds in the hearing-impaired ear) are closely related (i.e., are the same phenomena). The ramifications of this observation seem significant as they must impact our fundamental understanding of hearing and thus hearing loss [4], (p. 332, Allen90) [5]. In summary: Two-tone suppression acts like an automatic gain control, elevating the loudness threshold, with little audible distortion. We then discuss the properties of the CA, functionally measuring the CA gain. The URL for cited manuscripts:;
Original languageEnglish (US)
Article number020006
JournalAIP Conference Proceedings
Issue number1
StatePublished - Feb 27 2024


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