Auditory System: Structure

When the ancestors of land animals first left the sea, they faced many new challenges; one of which was the detection of airborne sounds. Animals have many types of vibration receptor but, like most cells in the body, they require a fluid environment. This posed a problem because, when sound waves meet a solid or liquid, most of the sound energy is reflected and less than 10% is transferred into the solid or liquid. This problem (impedance matching) has been overcome by the evolution of structures that take the highly dispersed energy of the air molecules and focus it onto a small solid point to produce vibrations in the fluid around the specialized vibration receptors. This entry describes the structure of the ear and the ...