부산대학교 도서관

The effect of different forms of longitudinal coupling on the active response of the cochlea are analysed using an elemental approach, based on a previous finite element model of the guinea pig cochlea that has three mechanical degrees of freedom. The overall basilar membrane (BM) admittance can be readily calculated using the elemental method, and since this is the only aspect of the organ of Corti dynamics that couples into the fluid, it is a useful indicator of its overall behaviour. As has been shown in previous studies, mechanical longitudinal coupling in the TM, together with 3D fluid coupling, are most important in obtaining a coupled BM frequency response that is both tall and broad, as observed in experimental data. An intuitive and efficient method is used for representing the longitudinal coupling in the fluid, by decomposing the 3D fluid coupling in the wavenumber domain into a local near-field mass loading of the organ of Corti and the analytically simpler 1D fluid coupling, representing long range fluid-structure coupling. The 3D fluid coupling is also necessary to obtain a phase variation that is consistent with experimental measurements. The model of the organ of Corti can be represented as a mechanical three degree of freedom system, and when it is locally reacting all the mechanical elements, and hence the BM admittance, are independent of the wavenumber. When longitudinal coupling is introduced in the TM, the stiffness and damping associated with the TM shear motion then depends on the wavenumber. Similarly, when the near field fluid coupling is associated with the BM mass in the mechanical model, this too is now a function of wavenumber. The model can then be used to calculate a wavenumber-dependent BM admittance, which can be combined with the simple analytical equation for 1D fluid coupling to give the dispersion equation for the waves in the coupled cochlea. [ABSTRACT FROM AUTHOR]