outer and middle ear quick learn Flashcards
outer ear structures
pinna (auricle), external auditory meatus (canal), and ends at tympanic membrane
outer ear function
conductive mechanism
physiology of external auditory canal
protective function
-achieved by anatomy (angled direction)
ear canal resonance
one lumped resonance based on sound pressure at various areas within the ear
average for an adult is 3000 hz
how does the external auditory canal act as a resonator
it is a closed (on one end) tube resonator
effects of the ear canal and resonance
the resonant frequency is based on tube length
-considered to be a tube that is closed on one end
-average ear canal has a resonant frequency of around 3000 Hz
effects of the ear canal and pinna combined on resonance
causes a slightly different sound pressure curve
-concha serves as a end correction and lowered the resonant frequency to around 2700 (17 dB) Hz
-produces a composite curve with two peaks (2700 and 5000 Hz)
middle ear structures
3 ossicles, muscles, TM, ET
middle ear divisions
epitympanum, mesotympanum, and hypotympanum
middle ear function
turns acoustic sound waves into mechanical vibrations
function of the ossicles and the TM
increased force is picked up by the TM and by the time it pushed on the footplate, there is enough force to push the fluids within the cochlea
middle ear impedance matching function
trying to match the amount of resistance in outer vs. inner ear
-lever action, area difference of the TM compared to stapes footplate and the buckling of the tympanic membrane
if we did not have the impedance matching, what would occur
we would lose around 99% of energy because it would bounce off the eardrum
how much gain occurs with impedance matching
33-34 dB
middle ear muscle reflex
contraction of the stapedius muscle occurs as a response to loud sounds
-protects our ear from our own voice
-stapedius muscle contracts 50 msec prior to vocalization
