Examining middle-ear and tectorial membrane mechanics using computational models

Abstract

The ear acts as a sensitive broadband receiver which transduces sound waves in the ear canal into electrical signals sent to the nervous system. The mechanics of the many small components which comprise the ear are fine-tuned to detect faint sound throughout a wide range of frequencies. By studying the mechanics of different components of the ear, the mechanisms which allow for such remarkable abilities can be better understood. In this thesis, the mechanics of components of the ears of several species are investigated: specifically, the mouse tectorial membrane (an extracellular matrix located in the inner ear), the chinchilla middle ear, and the bullfrog eardrum are studied. Previous experimental studies have revealed interesting phenomena in these components; this study aims to use computational models to clarify key aspects of the mechanics of these components. This thesis aims to characterize, for the first time, the anisotropic material properties of the tectorial membranes of wild-type and genetically modified mice at audio frequencies. Additionally, a circuit model of the chinchilla middle ear, absent in literature prior to this study, was developed. Using this model, this thesis aims to evaluate the influence of stiffness, damping, and inertial properties on middle-ear transmission characteristics. Lastly, in this thesis, a mechanical basis for the long group delay observed through the bullfrog eardrum is proposed.