Aspectos fisiologicos e fisicos da orelha como emissora de sons / Physics and physiological aspects of the ear as a sound emitter system

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Ear is the sound receptor in our body. Sound is captured and driven through external ear, amplified and modulated in middle ear and transduced to electrical sign in internal ear. However, otoacoustic emissions and objective tinnitus are examples of an inverse process, where ear can be a sound emitter. Trying to understand some of theses events, in which sound emission occurs, the physiology of hearing and the physical basis to the sound propagation through the ear was revised. It was used as main tool, articles of Web of Science, from the last 25 years. From this point, it was developed a theoretical model to the way of sound, generated inside cochlea that propagates in tympanic membrane direction. It was performed mathematical calculations to sound attenuation, caused by the mechanical inertia of oval window - ossicles - tympanic membrane structure. For that, it was considered the area ratio between oval window and tympanum and the lever action ossicular chain. We concluded that sound generation by electromotility of outer hair cells inside cochlea, is attenuated in 20 times when it passes through ossicular chain in the inverse way. Besides this lost in sound energy, it was also demonstrated that in perilymph-oval window interface sound transmission is considerable (70%), because there are not big differences between the acoustic impedances of involved structures. Then, in physical basis, it was shown how ear can emit sound from contraction of outer hair cells.

ASSUNTO(S)

orelha som zumbido emissões otoacusticas espontaneas spontaneous otoacoustic emissions sound ear tinnitus

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