Hearing at speech frequencies is different from what we thought

Guinan, John J.

doi:10.1113/jp274418

Cited by 8 publications

(3 citation statements)

References 4 publications

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“…That there is a discrepancy between AN tuning and OoC mechanical tuning in the low-frequency apex has been previously pointed out and hypothesized to be from filtering that occurs after the mechanical drive to IHCs (cf. (2,43)). An alternate possibility is that RL and TM motions become more similar as frequency decreases below CF, thereby producing a low-pass filter in the IHC mechanical drive.…”

Section: Probe Tones Lower In Frequency Than the Apicalbasal Transition: Effects Apical Of The Cfmentioning

confidence: 99%

The Spatial Origins of Cochlear Amplification Assessed by Stimulus-Frequency Otoacoustic Emissions

Goodman

Lee

Guinan

et al. 2020

Biophysical Journal

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Cochlear amplification of basilar membrane traveling waves is thought to occur between a tone's characteristic frequency (CF) place and within one octave basal of the CF. Evidence for this view comes only from the cochlear base. Stimulus-frequency otoacoustic emissions (SFOAEs) provide a noninvasive alternative to direct measurements of cochlear motion that can be measured across a wide range of CF regions. Coherent reflection theory indicates that SFOAEs arise mostly from the peak region of the traveling wave, but several studies using far-basal suppressor tones claimed that SFOAE components originate many octaves basal of CF. We measured SFOAEs while perfusing guinea pig cochleas from apex to base with salicylate or KCl solutions that reduced outer-hair-cell function and SFOAE amplification. Solution effects on inner hair cells reduced auditory nerve compound action potentials (CAPs) and provided reference times for when solutions reached the SFOAE-frequency CF region. As solution flowed from apex to base, SFOAE reductions generally occurred later than CAP reductions and showed that the effects of cochlear amplification usually peaked $1/2 octave basal of the CF region. For tones R2 kHz, cochlear amplification typically extended $1.5 octaves basal of CF, and the data are consistent with coherent reflection theory. SFOAE amplification did not extend to the basal end of the cochlea, even though reticular lamina motion is amplified in this region, which indicates that reticular lamina motion is not directly coupled to basilar membrane traveling waves. Previous reports of SFOAE-frequency residuals produced by suppressor frequencies far above the SFOAE frequency are most likely due to additional sources created by the suppressor. For some tones <2 kHz, SFOAE amplification extended two octaves apical of CF, which highlights that different vibratory motions produce SFOAEs and CAPs, and that the amplification region depends on the cochlear mode of motion considered. The concept that there is a single ''cochlear amplification region'' needs to be revised.

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Section: Probe Tones Lower In Frequency Than the Apicalbasal Transition: Effects Apical Of The Cfmentioning

confidence: 99%

The Spatial Origins of Cochlear Amplification Assessed by Stimulus-Frequency Otoacoustic Emissions

Goodman

Lee

Guinan

et al. 2020

Biophysical Journal

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“…Although significant differences between the AN fiber threshold tuning curves and mechanical tuning responses have long been appreciated below the characteristic frequency at high-frequency basal regions (Narayan et al 1998;Yoon et al 2011), our data showed that these differences are significantly greater in the low-frequency apical regions of the cochlea at the level of OoC. Ultimately, the alterations in the shape of the mechanical tuning curve enlarge the bandwidth so much that this frequency tuning is obviously broader than that of the AN fibers that innervate the IHCs in that region of the cochlea (Guinan 2017). Thus our data dispel the long-held notion that the electrochemical responses of AN fibers mirror the vibratory responses of the OoC.…”

Section: Discussionmentioning

confidence: 60%

Organ of Corti vibration within the intact gerbil cochlea measured by volumetric optical coherence tomography and vibrometry

Dong

Xia

Raphael

et al. 2018

Journal of Neurophysiology

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There is indirect evidence that the mammalian cochlea in the low-frequency apical and the more commonly studied high-frequency basal regions function in fundamentally different ways. Here, we directly tested this hypothesis by measuring sound-induced vibrations of the organ of Corti (OoC) at three turns of the gerbil cochlea using volumetric optical coherence tomography vibrometry (VOCTV), an approach that permits noninvasive imaging through the bone. In the apical turn, there was little frequency selectivity, and the displacement-vs.-frequency curves had low-pass filter characteristics with a corner frequency of ~0.5–0.9 kHz. The vibratory magnitudes increased compressively with increasing stimulus intensity at all frequencies. In the middle turn, responses were similar except for a slight peak in the response at ~2.5 kHz. The gain was ~50 dB at the peak and 30–40 dB at lower frequencies. In the basal turn, responses were sharply tuned and compressively nonlinear, consistent with observations in the literature. These data demonstrated that there is a transition of the mechanical response of the OoC along the length of the cochlea such that frequency tuning is sharper in the base than in the apex. Because the responses are fundamentally different, it is not appropriate to simply frequency shift vibratory data measured at one cochlear location to predict the cochlear responses at other locations. Furthermore, this means that the number of hair cells stimulated by sound is larger for low-frequency stimuli and smaller for high-frequency stimuli for the same intensity level. Thus the mechanisms of central processing of sounds must vary with frequency. NEW & NOTEWORTHY A volumetric optical coherence tomography and vibrometry system was used to probe cochlear mechanics within the intact gerbil cochlea. We found a gradual transition of the mechanical response of the organ of Corti along the length of the cochlea such that tuning at the base is dramatically sharper than that at the apex. These data help to explain discrepancies in the literature regarding how the cochlea processes low-frequency sounds.

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“…The two illustrated cases have opposite polarity with respect to one another at the same tb . In experimentally measured basilar membrane click responses, all the peaks measured from different locations along the cochlea approximately align in the same direction [31]. Therefore, this matching polarity (after accounting for scaled time) may also be used to determine possible B u , as well its variation along the length of the cochlea.…”

Section: A Integer B Umentioning

confidence: 99%

Design of FIR filters with magnitude specifications

Alkhairy¹

Conference Record of the Thirtieth Asilomar Conference on Signals, Systems and Computers

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In this paper, we present a method for the design of an FIR filter that minimizes the Chebyshev error in the magnitude frequency domain. The method exhibits desirable properties similar to those characterizing the Parks-McClellan algorithm and requires less than seven iterations to solve the nonlinear filter design problem. The O ( N 2 ) iterative method yields filters that are 40% better than those designed using conventional techniques and results in filters that are 30% shorter.

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Hearing at speech frequencies is different from what we thought

Cited by 8 publications

References 4 publications

The Spatial Origins of Cochlear Amplification Assessed by Stimulus-Frequency Otoacoustic Emissions

The Spatial Origins of Cochlear Amplification Assessed by Stimulus-Frequency Otoacoustic Emissions

Organ of Corti vibration within the intact gerbil cochlea measured by volumetric optical coherence tomography and vibrometry

Design of FIR filters with magnitude specifications

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