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Near field fluid coupling between internal motion of the organ of Corti and the basilar membrane

Near field fluid coupling between internal motion of the organ of Corti and the basilar membrane
Near field fluid coupling between internal motion of the organ of Corti and the basilar membrane
The pressure distribution in each of the fluid chambers of the cochlea can be decomposed into a 1D, or plane wave, component and a near field component, which decays rapidly away from the excitation point. The transverse motion of the basilar membrane, BM, for example, generates both a 1D pressure field, which couples into the slow wave, and a local near field pressure, proportional to the BM acceleration, that generates an added mass on the BM due to the fluid motion. When the organ of Corti, OC, undergoes internal motion, due for example to outer hair cell activity, this motion will not itself generate any 1D pressure if the OC is incompressible and the BM is constrained not to move volumetrically, and so will not directly couple into the slow wave. This motion will, however, generate a near field pressure, proportional to the OC acceleration, which will act on the OC and thus increases its effective mass. The near field pressure due to this OC motion will also act on the BM, generating a force on the BM proportional to the acceleration of the OC, and thus create a “coupling mass” effect. By reciprocity, this coupling mass is the same as that acting on the OC due to the motion of the BM. This near field fluid coupling is initially observed in a finite element model of a slice of the cochlea. These simulations suggest a simple analytical formulation for the fluid coupling, using higher order beam modes across the width of the cochlear partition. It is well known that the added mass due to the near field pressure dominates the overall mass of the BM, and thus significantly affects the micromechanical dynamics. This work not only quantifies the added mass of the OC due its own motion in the fluid, and shows that this is important, but also demonstrates that the coupling mass effect between the BM and OC significantly affects the dynamics of simple micromechanical models
50008
Elliott, Stephen J.
721dc55c-8c3e-4895-b9c4-82f62abd3567
Ni, Guangjian
f6ddc112-7d81-403a-b97a-7ecbc8fd4e59
Elliott, Stephen J.
721dc55c-8c3e-4895-b9c4-82f62abd3567
Ni, Guangjian
f6ddc112-7d81-403a-b97a-7ecbc8fd4e59

Elliott, Stephen J. and Ni, Guangjian (2015) Near field fluid coupling between internal motion of the organ of Corti and the basilar membrane. 12th International Workshop on the Mechanics of Hearing, Cape Sounio, Greece. 22 - 28 Jun 2014. p. 50008 . (doi:10.1063/1.4939353).

Record type: Conference or Workshop Item (Paper)

Abstract

The pressure distribution in each of the fluid chambers of the cochlea can be decomposed into a 1D, or plane wave, component and a near field component, which decays rapidly away from the excitation point. The transverse motion of the basilar membrane, BM, for example, generates both a 1D pressure field, which couples into the slow wave, and a local near field pressure, proportional to the BM acceleration, that generates an added mass on the BM due to the fluid motion. When the organ of Corti, OC, undergoes internal motion, due for example to outer hair cell activity, this motion will not itself generate any 1D pressure if the OC is incompressible and the BM is constrained not to move volumetrically, and so will not directly couple into the slow wave. This motion will, however, generate a near field pressure, proportional to the OC acceleration, which will act on the OC and thus increases its effective mass. The near field pressure due to this OC motion will also act on the BM, generating a force on the BM proportional to the acceleration of the OC, and thus create a “coupling mass” effect. By reciprocity, this coupling mass is the same as that acting on the OC due to the motion of the BM. This near field fluid coupling is initially observed in a finite element model of a slice of the cochlea. These simulations suggest a simple analytical formulation for the fluid coupling, using higher order beam modes across the width of the cochlear partition. It is well known that the added mass due to the near field pressure dominates the overall mass of the BM, and thus significantly affects the micromechanical dynamics. This work not only quantifies the added mass of the OC due its own motion in the fluid, and shows that this is important, but also demonstrates that the coupling mass effect between the BM and OC significantly affects the dynamics of simple micromechanical models

Other
1.4939353.pdf_expires=1455291684&id=id&accname=2103930&checksum=F27D064F3F006D9075B943B0EBB1A5AF - Accepted Manuscript
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More information

Published date: 2015
Venue - Dates: 12th International Workshop on the Mechanics of Hearing, Cape Sounio, Greece, 2014-06-22 - 2014-06-28
Organisations: Inst. Sound & Vibration Research, Signal Processing & Control Grp

Identifiers

Local EPrints ID: 387358
URI: http://eprints.soton.ac.uk/id/eprint/387358
PURE UUID: c3ff0297-8d57-432b-b272-0306f6272d2a
ORCID for Guangjian Ni: ORCID iD orcid.org/0000-0002-9240-3020

Catalogue record

Date deposited: 25 Feb 2016 09:45
Last modified: 10 Jan 2022 03:00

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Author: Guangjian Ni ORCID iD

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