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Periodic orbit techniques for mode shape approximation

Periodic orbit techniques for mode shape approximation
Periodic orbit techniques for mode shape approximation
If the active cochlear is modelled as having a uniform distribution of parameters, the system is stable even for high gains in the cochlear amplifiers, resulting in very significant active enhancements of its response, of the order of 90 dB. In a real biological system, however, such uniform distributions will always be disrupted by random spatial variations, and a state space model of the cochlea has been developed that can be used to investigate the effects of such random variations. One effect is found to be that the cochlear amplifier gains have to be reduced to maintain stability, so that maximum active enhancements of the cochlear response is more typically 40 dB. The cochlear amplifier, however, is nonlinear as well as active, and unstable poles in the linear model generate instabilities that settle into limit cycle oscillations at discrete frequencies in the nonlinear model. These oscillations are thought to be the origin of spontaneous otoacoustic emissions, and have a significant effect on sound detection at low level. At higher sound pressure levels the nonlinearity in the cochlear amplifier suppresses such oscillations and the sound detection has a more uniform frequency response, although the amplification is reduced.
0001-4966
p.3182
Ham, Christopher J.
cce8921f-ba0d-40fa-9815-3f3db9a5207f
Wright, M.C.M.
b7209187-993d-4f18-8003-9f41aaf88abf
Ham, Christopher J.
cce8921f-ba0d-40fa-9815-3f3db9a5207f
Wright, M.C.M.
b7209187-993d-4f18-8003-9f41aaf88abf

Ham, Christopher J. and Wright, M.C.M. (2007) Periodic orbit techniques for mode shape approximation. Journal of the Acoustical Society of America, 121 (5), p.3182.

Record type: Article

Abstract

If the active cochlear is modelled as having a uniform distribution of parameters, the system is stable even for high gains in the cochlear amplifiers, resulting in very significant active enhancements of its response, of the order of 90 dB. In a real biological system, however, such uniform distributions will always be disrupted by random spatial variations, and a state space model of the cochlea has been developed that can be used to investigate the effects of such random variations. One effect is found to be that the cochlear amplifier gains have to be reduced to maintain stability, so that maximum active enhancements of the cochlear response is more typically 40 dB. The cochlear amplifier, however, is nonlinear as well as active, and unstable poles in the linear model generate instabilities that settle into limit cycle oscillations at discrete frequencies in the nonlinear model. These oscillations are thought to be the origin of spontaneous otoacoustic emissions, and have a significant effect on sound detection at low level. At higher sound pressure levels the nonlinearity in the cochlear amplifier suppresses such oscillations and the sound detection has a more uniform frequency response, although the amplification is reduced.

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Published date: May 2007

Identifiers

Local EPrints ID: 50457
URI: http://eprints.soton.ac.uk/id/eprint/50457
ISSN: 0001-4966
PURE UUID: 8cf7aa92-11f0-4925-b47c-8a5f11d25cda
ORCID for M.C.M. Wright: ORCID iD orcid.org/0000-0001-9393-4918

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Date deposited: 27 Feb 2008
Last modified: 11 Jan 2023 02:34

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Contributors

Author: Christopher J. Ham
Author: M.C.M. Wright ORCID iD

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