Fluid coupling and waves in the cochlea

Abstract

The cochlea plays an important role in human hearing. Its basic function is to map sounds of different frequencies onto corresponding characteristic positions on the basilar membrane, BM. When sounds enter the fluid-filled cochlea, deflections of the BM occur due to pressure differences between the cochlear fluid chambers. These deflections propagate along the cochlea to a frequency-dependent characteristic position and then decay away rapidly. The mechanics of the cochlea are modelled using both analytic and numerical models. In this thesis, the passive response of the cochlea is analysed, corresponding to its behaviour at high sound levels, to study the fluid coupling and waves in the cochlea.

The fluid coupling is studied in 1D and 3D, uniform and non-uniform, uncoiled and coiled geometries, all with a passive basilar membrane. A ‘uniaxial model’, which is dependent on only a single dimension, is developed to represent the three-dimensional cochlea. The finite element method is also used to provide an independent check of the results from the analytic model.

Analytic methods are used to predict waves due to different mechanisms in the passive cochlea, such as 1D and 3D fluid coupling and longitudinal BM dynamics. The wave finite element, WFE, method is then used to decompose the results of a full finite element model of the coupled cochlea into wave components. Results show that apart from the conventional slow wave, other additional types of wave in the passive cochlea do not appear to play a dominant role in normal passive cochlear function.

More information

Identifiers

Catalogue record

Export record