CMD 278 Lecture Notes - Lecture 7: Vestibular Duct, Ossicles, Ear Canal
Document Summary
Vibration of air molecules in air leads to vibration of air molecules in the external auditory canal: sound is traveling in the medium of air. Perilymph in scala vestibuli moves in a wave-like motion: medium is now a liquid. Change of medium : leads to loss of sound intensity as sound moves from a low impedance medium (air) to a higher impedance medium (liquid) About 35 dbspl of sound is lost in transition: the unique properties of the ossicular chain offset this intensity loss. Ossicles act as a lever, get back about 2 db. Size ratio of tm to oval window: on average = 17:1, get back about 25 db. Movement of perilymph causes : movement of reissner"s membrane, which moves endolymph, which moves basilar membrane, which moves perilymph in scala tympani, which pushes out the round window, and then everything moves in the opposite direction.
