The aim of this project theme is to develop and test models that capture the essential mechanics of the cochlea in humans. The models are constructed using estimates of mechanical properties of cochlear components, and formulations of the governing laws of motion. The model predictions are tested against available measurements of mechanical vibrations of cochlear components, and measurements of OAEs.
When we listen to sounds, the cochlea first acts on the resulting mechanical vibrations as a sensitive and sharply tuned nonlinear filter bank, before it then transduces the vibrations into neural impulses. This remarkably sharp tuning appears to be achieved by a complicated pattern of motion involving the cochlear fluids, the organ of Corti, the tectorial membrane, and, crucially, active amplification via the outer hair cells. The aim of this project theme is to develop and test models that capture the essential mechanics of the cochlea in humans. The models are constructed using estimates of mechanical properties of cochlear components, and formulations of the governing laws of motion. The model predictions are tested against available measurements of mechanical vibrations of cochlear components, and measurements of OAEs. It is anticipated that the models will help to answer some of the key outstanding questions in cochlear mechanics: How do the outer hair cells amplify the travelling wave? What is the role of the tectorial membrane in the mechanics? Does the cochlear amplifier give rise to a feed-forward control system? Does the cochlea require systems to maintain a high level of amplification while avoiding major system instabilities? What role does the efferent system play in cochlear mechanics? How do cochlear pathologies alter the mechanics? Current and planned modelling work includes: examining the generation of, and interactions between, multiple spontaneous OAEs; modelling the characteristics of distortion product OAEs from both distortion-source and reflection-source mechanisms; and modelling abnormal tectorial membranes, which arise from certain genetic abnormalities, and for which data on basilar membrane vibrations are available.