Input impedance of the cochlea in cat

Lynch, Thomas J.; Nedzelnitsky, Victor; Peake, William T.

doi:10.1121/1.387995

Cited by 180 publications

(153 citation statements)

References 25 publications

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“…Increasing Poisson_s ratio to 0.4 for the soft tissues in this model produced displacement changes of less than 10%, consistent with previous modeling (e.g., Qi et al 2004). This is also consistent with the theoretical relationship G = E/2(1 + u) between Poisson_s ratio (u), Young_s modulus (E), and the shear modulus (G), and the assumption that the annular ligament primarily operates in shear (Lynch et al 1982). This relationship predicts that the effect of increasing Poisson_s ratio to 0.5 would be only about 15% for the annular ligament.…”

Section: Geometry and Materials Propertiessupporting

confidence: 87%

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Low-Frequency Finite-Element Modeling of the Gerbil Middle Ear

Elkhouri

Liu

Funnell

2006

JARO

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The gerbil is a popular species for experimental middle-ear research. The goal of this study is to develop a 3D finite-element model to quantify the mechanics of the gerbil middle ear at low frequencies (up to about 1 kHz). The 3D reconstruction is based on a magnetic resonance imaging dataset with a voxel size of about 45 mm, and an x-ray micro-CT dataset with a voxel size of about 5.5 mm, supplemented by histological images. The eardrum model is based on moiré shape measurements. Each individual structure in the model was assumed to be homogeneous with isotropic, linear, and elastic material properties derived from a priori estimates in the literature. The behavior of the finite-element model in response to a uniform acoustic pressure on the eardrum of 1 Pa is analyzed. Sensitivity tests are done to evaluate the significance of the various parameters in the finiteelement model. The Young_s modulus and the thickness of the pars tensa have the most significant effect on the load transfer between the eardrum and the ossicles and, along with the Young_s modulus of the pedicle and stapedial annular ligament, on the displacements of the stapes. Overall, the model demonstrates good agreement with low-frequency experimental data. For example, (1) the maximum footplate displacement is about 35 nm; (2) the umbo/stapes displacement ratio is found to be about 3.5; (3) the motion of the stapes is predominantly piston-like; and (4) the displacement pattern of the eardrum shows two points of maximum displacement, one in the posterior region and one in the anterior region. The effects of removing or stiffening the ligaments are comparable to those observed experimentally.

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Section: Geometry and Materials Propertiessupporting

confidence: 87%

“…The lateral bundle is about 160 mm in height and 50 mm in length, and its width varies between about 130 and 200 mm. The Young_s modulus of the SAL was set to 10 kPa, in line with vestibular sound pressure measurements by Lynch et al (1982). This value was also used by Sun et al (2002).…”

Section: Geometry and Materials Propertiesmentioning

confidence: 99%

Low-Frequency Finite-Element Modeling of the Gerbil Middle Ear

Elkhouri

Liu

Funnell

2006

JARO

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“…We assumed the Young's modulus of the stapedial annular ligament to be 10 kPa, as estimated by Lynch et al (1982) in the cat. A recent measurement by Gan et al (2011) in human temporal bones reported a shear modulus of 3.6 kPa for the smallest measured shear stress.…”

Section: Baseline Materials Propertiesmentioning

confidence: 99%

Finite-Element Modelling of the Response of the Gerbil Middle Ear to Sound

Maftoon

Funnell

Daniel

et al. 2015

JARO

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We present a finite-element model of the gerbil middle ear that, using a set of baseline parameters based primarily on a priori estimates from the literature, generates responses that are comparable with responses we measured in vivo using multi-point vibrometry and with those measured by other groups. We investigated the similarity of numerous features (umbo, pars-flaccida and pars-tensa displacement magnitudes, the resonance frequency and break-up frequency, etc.) in the experimental responses with corresponding ones in the model responses, as opposed to simply computing frequency-by-frequency differences between experimental and model responses. The umbo response of the model is within the range of variability seen in the experimental data in terms of the low-frequency (i.e., well below the middle-ear resonance) magnitude and phase, the main resonance frequency and magnitude, and the roll-off slope and irregularities in the response above the resonance frequency, but is somewhat high for frequencies above the resonance frequency. At low frequencies, the ossicular axis of rotation of the model appears to correspond to the anatomical axis but the behaviour is more complex at high frequencies (i.e., above the pars-tensa break-up). The behaviour of the pars tensa in the model is similar to what is observed experimentally in terms of magnitudes, phases, the break-up frequency of the spatial vibration pattern, and the bandwidths of the high-frequency response features. A sensitivity analysis showed that the parameters that have the strongest effects on the model results are the Young's modulus, thickness and density of the pars tensa; the Young's modulus of the stapedial annular ligament; and the Young's modulus and density of the malleus. Displacements of the tympanic membrane and manubrium and the lowfrequency displacement of the stapes did not show large changes when the material properties of the incus, stapes, incudomallear joint, incudostapedial joint, and posterior incudal ligament were changed by ±10 % from their values in the baseline parameter set.

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“…6) incorporates the measurements of the geometry of the ear canal (37), the 3D asymmetrical geometry of the eardrum (3), the details of the eardrum fiber structure (11), a simple lever model for the ossicles terminated by known values for the cochlear impedance (38), and radiation damping representing the open middle-ear cavity.…”

Section: Methodsmentioning

confidence: 99%

The discordant eardrum

Fay¹,

Puria

Steele³

2006

Proc. Natl. Acad. Sci. U.S.A.

124

141

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At frequencies above 3 kHz, the tympanic membrane vibrates chaotically. By having many resonances, the eardrum can transmit the broadest possible bandwidth of sound with optimal sensitivity. In essence, the eardrum works best through discord. The eardrum's success as an instrument of hearing can be directly explained through a combination of its shape, angular placement, and composition. The eardrum has a conical asymmetrical shape, lies at a steep angle with respect to the ear canal, and has organized radial and circumferential collagen fiber layers that provide the scaffolding. Understanding the role of each feature in hearing transduction will help direct future surgical reconstructions, lead to improved microphone and loudspeaker designs, and provide a basis for understanding the different tympanic membrane structures across species. To analyze the significance of each anatomical feature, a computer simulation of the ear canal, eardrum, and ossicles was developed. It is shown that a cone-shaped eardrum can transfer more force to the ossicles than a flat eardrum, especially at high frequencies. The tilted eardrum within the ear canal allows it to have a larger area for the same canal size, which increases sound transmission to the cochlea. The asymmetric eardrum with collagen fibers achieves optimal transmission at high frequencies by creating a multitude of deliberately mistuned resonances. The resonances are summed at the malleus attachment to produce a smooth transfer of pressure across all frequencies. In each case, the peculiar properties of the eardrum are directly responsible for the optimal sensitivity of this discordant drum.collagen fibers ͉ hearing sensitivity ͉ middle ear ͉ transducers T he function of the middle ear in terrestrial mammals is to transfer acoustic energy between the air of the ear canal to the fluid of the inner ear. The first and crucial step of the transduction process takes place at the tympanic membrane, which converts sound pressure in the ear canal into vibrations of the middle ear bones. Understanding how the tympanic membrane manages this task so successfully over such a broad range of frequencies has been a subject of research since Helmholtz's publication in 1868 (1, 2).Even though the function of the eardrum is clear and the anatomy of the eardrum is well characterized, the connection between the anatomical features and the ability of the eardrum to transduce sound has been missing. The missing structurefunction relationships can be summarized by the following three questions. Why does the mammalian eardrum have its distinctive conical and toroidal shape? What is the advantage of its angular placement in the ear canal? What is the significance of its highly organized radial and circumferential fibers?The shape of the human and feline eardrum is known from detailed Moiré interferometry contour maps (refs. 3 and 4 and Fig. 1a). From the contour maps, three-dimensional reconstructions reveal the striking similarity of the two eardrums. In both cases, the eardrum has an ell...

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Input impedance of the cochlea in cat

Cited by 180 publications

References 25 publications

Low-Frequency Finite-Element Modeling of the Gerbil Middle Ear

Low-Frequency Finite-Element Modeling of the Gerbil Middle Ear

Finite-Element Modelling of the Response of the Gerbil Middle Ear to Sound

The discordant eardrum

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