Experimental observations of a mechanical cochlear model

Chadwick, Richard S.; Adler, Dan

doi:10.1121/1.380718

Cited by 5 publications

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“…The author showed frequencyposition mapping over 25-800 Hz band and maximum phase accumulation of 4π radians. Chadwick and Adler [8] built a 630 mm long cochlear model with constant dimensions. The model uses isotropic beams to represent BM.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of a Hydromechanical Scale Model of the Gerbil Cochlea

Liu

Gauthier

Mandelup

et al. 2008

Volume 11: Mechanical Systems and Control

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In this research, an uncoiled scale gerbil cochlea is designed and fabricated. The cochlea model is an uncoiled, 16 times scale model of the real gerbil cochlea and has only one duct. Both the basilar membrane width and the duct size vary along the length of the device, in analogy to the physiology. The cochlea duct is filled with silicone oil and driven by a modal exciter (shaker) at different frequencies. The movement of the basilar membrane is measured using laser vibrometry at different locations along the basilar membrane. The ratio of the basilar membrane velocity to drive velocity is computed and plotted. The characteristic frequency of the model varies from 7000 Hz at 2 cm from the base of the cochlea to 350 Hz at the 15 cm from the base. Two different viscosities silicone oil, 20 cSt and 500 cSt are used for the basilar membrane movement measurements. A WKB method is applied to the calculation of the basilar membrane movement of the scale cochlea model, in which the fluid motion is fully three dimensional.

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Section: Introductionmentioning

confidence: 99%

Experimental Investigation of a Hydromechanical Scale Model of the Gerbil Cochlea

Liu

Gauthier

Mandelup

et al. 2008

Volume 11: Mechanical Systems and Control

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“…Direct experimental measurements of cochlear function are difficult to obtain due to the inaccessibility of the cochlea and the delicate structure of the basilar membrane. Consequently, modeling is a particularly useful tool, and many models (mechanical [29]- [36], electrical [37]- [45] and mathematical [46]- [80]) have been developed (see Appendix). Difficulties notwithstanding, experimental data on the function of the cochlea has been painstakingly and ingeniously obtained.…”

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confidence: 99%

“…In order to check the assumptions used in deriving the equations of motion, experiments were conducted with a mechanical facsimile of this cochlear model [36].…”

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confidence: 99%

“…The oscillations of the basilar membrane model(31) can, again, be represented conveniently by(34) r/(x, t) r/sT(X, t) + rtTR(X, t), where the subscripts ST and TR denote the steady-state and transient parts, respectively. In particular,(35) r/sT(X, t) al(x) sin tot + az(x) cos tot where(36) ai (x) din sin nTrx/L,1, 2. More conveniently,(37)where and (38)r/ST(X, t) A(x) sin (tot + O(x)) O(x) sin -1 a2(x)/A(x) cos -1 al(X)/A(x) A(x) [a12(x) + a(x)] 1/2.That is, fisT(X, t) consists of traveling waves having a maximum amplitude A (x).…”

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Cochlear Dynamics: The Evolution of a Mathematical Model

Inselberg¹

1978

SIAM Rev.

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The evolution of a mathematical model designed to clarify the relationship between the structure and the function of the cochlea (inner ear) is traced. Starting from physical (rather than empirical) considerations, the mathematical description of each model is derived in terms of well-defined physical properties of the cochlea. Initially, the basilar membrane is modeled as a uniform simply supported beam vibrating in a viscous medium, and driven by a concentrated oscillating moment at the basal end. In such a system traveling and standing waves (transients) occur simultaneously. An analysis of the traveling waves reveals a place principle. The model has high and low frequency "thresholds" (i.e., at very high and very low frequencies, frequency discrimination diminishes). The model suggests that the fluid properties play a particularly important role at high frequencies, while the role of cochlear geometry becomes dominant at low frequencies. In the second stage, the beam is enclosed in a rectangular "cochlea" divided into two equal chambers and filled with viscous and incompressible fluid (the perilymph) communicating through a small opening at one end (the helicotrema). At the opposite end, the system is driven by a piston-like periodic forcing (i.e., the movement of the stapes in the middle ear). It is assumed that the oscillations of the basilar membrane have long wavelengthmcompared with the cochlear chamber heightmand that a thin unsteady boundary layer forms on all surfaces within the cochlea. In general, the results confirm and improve the results of the previous model. The place principle exhibited by this model corresponds well with experimental data at higher frequencies, but not at low frequencies. For good low frequency response, the model must be endowed with much of the cochlea's intricate geometry. This is done in the third model where the basilar membrane is represented by a wedge-shaped isotropic plate of constant thickness and enclosed by an arbitrary surface of revolution representing the cochlear shell. The plate is simply supported along its long edges while three different boundary conditions are considered for the support at the helicotrema. So as to emulate the presence of the cochlear duct (third cochlear chamber), a pressure difference in the fluid at the helicotrema is included. As in the second model, the cochlear fluids are taken to be viscous and incompressible, and the system is driven by periodic forcing at one end. The solution of the equations of motion as the input frequency tends to zero is obtained. The role of the basilar membrane taper, as well as cochlear cross-section's opposing taper, is delimited. The third chamber (cochlear duct) must be included in the model in order to utilize the full length of the basilar membrane for frequency discrimination. Consequently, the boundary conditions of the basilar membrane at the helicotrema can be analyzed, and it is shown that an elastic support (representing a "ligament") is required at the helicotrema.

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Analytical and numerical modeling of the hearing system: Advances towards the assessment of hearing damage

et al. 2017

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Hearing is an extremely complex phenomenon, involving a large number of interrelated variables that are difficult to measure in vivo. In order to investigate such process under simplified and well-controlled conditions, models of sound transmission have been developed through many decades of research. The value of modeling the hearing system is not only to explain the normal function of the hearing system and account for experimental and clinical observations, but to simulate a variety of pathological conditions that lead to hearing damage and hearing loss, as well as for development of auditory implants, effective ear protections and auditory hazard countermeasures. In this paper, we provide a review of the strategies used to model the auditory function of the external, middle, inner ear, and the micromechanics of the organ of Corti, along with some of the key results obtained from such modeling efforts. Recent analytical and numerical approaches have incorporated the nonlinear behavior of some parameters and structures into their models. Few models of the integrated hearing system exist; in particular, we describe the evolution of the Auditory Hazard Assessment Algorithm for Human (AHAAH) model, used for prediction of hearing damage due to high intensity sound pressure. Unlike the AHAAH model, 3D finite element models of the entire hearing system are not able yet to predict auditory risk and threshold shifts. It is expected that both AHAAH and FE models will evolve towards a more accurate assessment of threshold shifts and hearing loss under a variety of stimuli conditions and pathologies.

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Experimental observations of a mechanical cochlear model

Cited by 5 publications

References 0 publications

Experimental Investigation of a Hydromechanical Scale Model of the Gerbil Cochlea

Experimental Investigation of a Hydromechanical Scale Model of the Gerbil Cochlea

Cochlear Dynamics: The Evolution of a Mathematical Model

Analytical and numerical modeling of the hearing system: Advances towards the assessment of hearing damage

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