Periodic orbit techniques for mode shape approximation

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.


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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.

Item Type: Article
ISSNs: 0001-4966 (print)
Related URLs:
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Q Science > QP Physiology
Divisions : University Structure - Pre August 2011 > Institute of Sound and Vibration Research > Fluid Dynamics and Acoustics
ePrint ID: 50457
Accepted Date and Publication Date:
May 2007Published
Date Deposited: 27 Feb 2008
Last Modified: 31 Mar 2016 12:28

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