The cochlea as a smart structure

Elliott, Stephen J. and Shera, Christopher A. (2012) The cochlea as a smart structure. Smart Materials and Structures, 21, (6), 064001. (doi:10.1088/0964-1726/21/6/064001).


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The cochlea is part of the inner ear and its mechanical response provides us with many aspects of our amazingly sensitive and selective hearing. The human cochlea is a coiled tube, with two main fluid chambers running along its length, separated by a 35 mm-long flexible partition
that has its own internal dynamics. A dispersive wave can propagate along the cochlea due to the interaction between the inertia of the fluid and the dynamics of the partition. This partition includes about 12 000 outer hair cells, which have different structures, on a micrometre and a
nanometre scale, and act both as motional sensors and as motional actuators. The local feedback action of all these cells amplifies the motion inside the inner ear by more than 40 dB at low sound pressure levels. The feedback loops become saturated at higher sound pressure levels, however, so that the feedback gain is reduced, leading to a compression of the dynamic range in the cochlear amplifier. This helps the sensory cells, with a dynamic range of only
about 30 dB, to respond to sounds with a dynamic range of more than 120 dB. The active and nonlinear nature of the dynamics within the cochlea give rise to a number of other phenomena, such as otoacoustic emissions, which can be used as a diagnostic test for hearing problems in newborn children, for example. In this paper we view the mechanical action of the cochlea as a smart structure. In particular a simplified wave model of the cochlear dynamics is reviewed
that represents its essential features. This can be used to predict the motion along the cochlea when the cochlea is passive, at high levels, and also the effect of the cochlear amplifier, at low levels.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1088/0964-1726/21/6/064001
ISSNs: 0964-1726 (print)
1361-665X (electronic)
Subjects: R Medicine > RF Otorhinolaryngology
Divisions : Faculty of Engineering and the Environment > Institute of Sound and Vibration Research > Signal Processing & Control Research Group
ePrint ID: 339930
Accepted Date and Publication Date:
30 May 2012Published
Date Deposited: 01 Jun 2012 14:57
Last Modified: 31 Mar 2016 14:29

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