Evidence of mechanical nonlinearity and frequency selective wave amplification in the cochlea

Kemp, David T.

doi:10.1007/bf00455222

Cited by 490 publications

(233 citation statements)

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“…Cochlear responses are enhanced at frequencies for which the round-trip delay of the forward and reverse traveling OAE energy is an integer number of cycles, producing local peaks in sensitivity (i.e., threshold minima). Provided sufficient round-trip amplification, self-sustaining standing waves are generated at these same frequencies, which may be detected in the ear canal as SOAEs (Kemp 1979b;Wilson 1980;Zwicker and Schloth 1984). The frequency correspondence between SOAEs and threshold minima, as well as the common dependence of these phenomena on cochlear amplification, has been demonstrated experimentally (Long and Tubis 1988a, b;Furst et al 1992).…”

Section: Introductionmentioning

confidence: 92%

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Dewey

Lee

Dhar

2014

JARO

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Medial olivocochlear (MOC) influence on cochlear mechanics can be noninvasively, albeit indirectly, explored via the effects of contralateral acoustic stimulation (CAS) on otoacoustic emissions. CASmediated effects are particularly pronounced for spontaneous otoacoustic emissions (SOAEs), which are typically reduced in amplitude and shifted upward in frequency by CAS. We investigated whether similar frequency shifts and magnitude reductions were observed behaviorally in the fine structure of puretone hearing thresholds, a phenomenon thought to share a common underlying mechanism with SOAEs. In normal-hearing listeners, fine-resolution thresholds were obtained over a narrow frequency range centered on the frequency of an SOAE, both in the absence and presence of 60-dB SPL broadband CAS. While CAS shifted threshold fine structure patterns and SOAEs upward in frequency by a comparable amount, little reduction in the presence or depth of fine structure was observed at frequencies near those of SOAEs. In fact, CAS typically improved thresholds, particularly at threshold minima, and increased fine structure depth when reductions in the amplitude of the associated SOAE were less than 10 dB. Additional measurements made at frequencies distant from SOAEs, or near SOAEs that were more dramatically reduced in amplitude by the CAS, revealed that CAS tended to elevate thresholds and reduce threshold fine structure depth. The results suggest that threshold fine structure is sensitive to MOC-mediated changes in cochlear gain, but that SOAEs complicate the interpretation of threshold measurements at nearby frequencies, perhaps due to masking or other interference effects. Both threshold fine structure and SOAEs may be significant sources of intersubject and intrasubject variability in psychoacoustic investigations of MOC function.

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Section: Introductionmentioning

confidence: 92%

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Dewey

Lee

Dhar

2014

JARO

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“…The aforementioned observation of a spontaneous BM oscillation (SBMO) and a coincident spontaneous otoacoustic emission (SOAE) with the same frequency considerably strengthens this opinion. It has been proposed that in mammals SOAEs are due to longitudinal inhomogeneities of the organ of Corti, which cause multiple internal reflections in the cochlea (Kemp 1978(Kemp , 1979Shera 2003). The same explanation should be true for spontaneous oscillations of the basilar membrane.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Basilar-Membrane Oscillation (SBMO) and Coherent Reflection

Boer

Nuttall

2006

JARO

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In a previous report (in JARO) we have described a relatively high-frequency (15 kHz) spontaneous oscillation of the basilar membrane (SBMO) in a guinea pig ear; this oscillation was accompanied by a spontaneous otoacoustic emission (SOAE) at the same frequency. During the spontaneous oscillation and after it had subsided, the mechanical frequency response of the basilar membrane was measured by way of a wide-band random-noise stimulus, and it showed a number of spectral peaks, one of which having the frequency of the original oscillation. This pattern of peaks cannot be explained by assuming a single place of reflection in the cochlea. In this paper the process of Fcoherent reflection_ is artificially evoked in a three-dimensional model of the cochlea by imposing random place-fixed irregularities to the basilar-membrane impedance. It is shown that in the model a series of peaks arises in the frequency spectrum of the basilar-membrane response which phenomenon resembles the one found in the experimental animal. It is also shown that these peaks are actually due to superposition of the primary wave and a wave resulting from Fcoherent reflection_ which is reflected at the stapes. When the intensity of the acoustic stimulus signal is increased, the relative sizes of these peaks in the simulation diminish in about the same way as in the experiment.It is concluded that coherent reflection most likely is the cause of the Fextra peaks_, and that this concept can also explain the observed level dependence of these peaks. The findings of this study lead to a minor refinement regarding the actual requirements for coherent reflection to arise.

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“…Two-tone distortion products are also known as combination tones, because their pitches match combinations of the primary frequencies (f 1 and f 2 , f 2 > f 1 ), such as f 2 -f 1 , (n + 1)f 1 -nf 2 and (n + 1)f 2 -nf 1 (n = 1,2,3 …) (refs 2-4). Physiological correlates of the perceived distortion products exist in responses of auditory-nerve fibres [5][6][7][8] and inner hair cells 9 and in otoacoustic emissions (sounds generated by the cochlea, recordable at the ear canal) 7,[10][11][12] . Because the middle ear responds linearly to sound 13,14 and neural responses to distortion products can be abolished by damage to hair cells at cochlear sites preferentially tuned to the frequencies of the primary tones 8 , it was hypothesized that distortion products are generated at these sites and propagate mechanically along the basilar membrane to the location tuned to the distortion-product frequency 7,8 .…”

Section: Introductionmentioning

confidence: 99%

Two-tone distortion in the basilar membrane of the cochlea

Robles

Ruggero

Rich

1991

Nature

166

101

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When humans listen to pairs of thnes they hear additional tones, or distortion products, that are not present in the stimulus 1 . Two-tone distortion products are also known as combination tones, because their pitches match combinations of the primary frequencies (f 1 and f 2 , f 2 > f 1 ), such as f 2 -f 1 , (n + 1)f 1 -nf 2 and (n + 1)f 2 -nf 1 (n = 1,2,3 …) (refs 2-4). Physiological correlates of the perceived distortion products exist in responses of auditory-nerve fibres [5][6][7][8] and inner hair cells 9 and in otoacoustic emissions (sounds generated by the cochlea, recordable at the ear canal) 7,[10][11][12] . Because the middle ear responds linearly to sound 13,14 and neural responses to distortion products can be abolished by damage to hair cells at cochlear sites preferentially tuned to the frequencies of the primary tones 8 , it was hypothesized that distortion products are generated at these sites and propagate mechanically along the basilar membrane to the location tuned to the distortion-product frequency 7,8 . But until now, efforts to confirm this hypothesis have failed 15,16 . Here we report the use of a new laser-velocimetry technique 17 to demonstrate two-tone distortion in basilarmembrane motion at low and moderate stimulus intensities.The response of the basilar membrane to two equal-intensity tones was measured at the basal turn of the cochlea in anaesthetized chinchillas. Distortion-product data presented here from a single chinchilla (L17) are representative of similar observations in cochleae from six animals. Figure 1 displays frequency spectra of basilar-membrane responses to primary tones presented at intensities ranging from 60 to 90 dB SPL (decibels 'sound pressure level'; that is, referenced to 20 μPa). In addition to peaks at the primary frequencies (7.08 and 7.79 kHz), the spectra include several peaks at distortion-product frequencies both lower and higher than the primary frequencies, such as 2f 1 -f 2 and 2f 2 -f 1 . The number and amplitude of spectral peaks in the responses vary in a complex manner with the intensity of the twotone stimuli. The absolute amplitude of some of the peaks actually decreases as the intensity of the primary tones increases from 70 to 90 dB SPL. Figure 2a illustrates magnitudes of the 2f 1 -f 2 and 2f 2 -f 1 distortion products as a function of stimulus intensity. The magnitudes of the distortion products increased with the level of the primary tones up to 80 dB SPL, whereupon they reached a plateau or decreased with further increases in stimulus level. Figure 2a also shows the dependence on intensity of responses to a single tone at the distortion-product frequency (equal to the characteristic frequency, 8.5 kHz). This curve was used to compute the distortion-product 'effective level': the intensity of a single tone at the distortion-product frequency required to evoke a response of the same magnitude as the distortion product produced by a two-tone stimulus. Distortion-product effective levels (Fig. 2b) were highest at the lowest stimulus...

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Evidence of mechanical nonlinearity and frequency selective wave amplification in the cochlea

Cited by 490 publications

References 10 publications

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Spontaneous Basilar-Membrane Oscillation (SBMO) and Coherent Reflection

Two-tone distortion in the basilar membrane of the cochlea

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