Hearing Physiology W10 Flashcards
what does hearing have to do with slt?
necessary for development of oral communication major component of communication - impairment can result in communication break down can result in delayed speech and language acquisition, academic, social isolation
human hearing range
normal 20-20 000 Hz, most sensitive at 126-8 000 Hz humans can detect sounds from 0dB to 140dB higher freq require greater intensity to be audible
localisation of sound
2 ears - one side receives sound faster at a greater intensity and with a greater freq spectrum
nuclei of brain receive input from both ears for comparison of this info
this tells the brain which side of the body the sound source is
auricle/pinna acts as a directional microphone allows us to filter background noise, dampens sounds that occur behind us
functions of the peripheral auditory system
out ear - collects and funnels to middle ear, conduction
middle ear - impedence matching, improves transition to inner ear, transformation of acoustic pressure waves to mechanical energy
inner ear - converts sound to electrical impulse for neural recognition, frequency distinction, changes mechanical energy into neural impulse
why amplify sound through ear?
impedence mismatch, air of outer ear and fluid of inner ear, resistance of air and fluid so different that only 1/10th of the sound would transmit from air to fluid
therefore auditory system must reduce this mismatch to achieve greater sound transmission
3 mechanisms of amplification
outer ear - collection bowl and closed tube (tympanic membrane) that resonates speech freq and amplifies the sound by 5 to 20 dB
ossicular chain - leverage power of ossicular chain multiplies tympanic vibration slightly by 2dB
ear drum > stapes - difference in size between tympanic membrane and footplate of stapes, amplifies sound up to 25dB
protection mechanisms of middle ear
acoustic reflex - stiffens the ossicular chain to protect from loud sounds
stapedius muscle attached to stapes, tensor tympani attached to malleus
prevents excessive vibration of stapes into oval window to protect cochlea - too slow for some sounds
inner ear
basilar memebrane vibrates - hair cells convert vibrations to electrical impulses - inner hair cells provide neural signal - outer hair cells amplify neural signal - auditory nerve carries electrical impulses to brain
how do we perceive different sound?
different freq displace different parts of the basilar membrance
apical end - lower frew
basialr end - higher freq
tonotopical organisation of the organ of corti
