HSC 350 Lecture Notes - Lecture 5: Interaural Time Difference, Dorsal Cochlear Nucleus, Sound Localization
Document Summary
The external ear gathers sound energy and focuses it on the eardrum (tympanic membrane). The middle ear functions to ensure transmission of sound energy across the air-fluid boundary by matching the low-impedance airborne sounds to the higher-impedance fluid filled inner ear (impedance describes a medium"s resistance to movement). Normally, when sound waves travel from a low-impedance medium like air to a much higher impedance medium like water, almost all of the acoustical energy is reflected. The cochlea (latin; snail) of the inner ear is the site where the energy from sonically generated pressure waves is transformed into neural impulses. This occurs because sound waves displace the fluid in the inner ear and vibrate inner membrane structures that initiate sensory transduction by displacing hair cells located there. One product of the process of acoustical decomposition is the systematic representation of sound frequency along the length of the cochlea, referred to as tonotopy, which is preserved throughout the central auditory pathway.
