the ear

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  • the physics of the ear
    • the outer ear
      • externa auditory meatus
      • typanic membrane
      • pinna
      • cerumious glands
    • the middle ear
      • typpanic cavity
      • auditory ossicles - 3 small bones
        • hammer connects ear drum and anvil
      • round window
      • function = to amplify sound waves
        • bones rock and transfer energy via cavity
          • amplitude x1.5
        • large area diff ear drum vs oval window
          • increases pressure x 15
        • p of sound waves = x 20
    • inner ear
      • balance organs detect orientation and velocity chnages
      • cochlea- helical 3 membrane channels
        • 3rd = 25,000 hairs corti
        • tympanic - fluid filled
    • hearing
      • sound exists as pressure waves in air
      • p waves cause ear drum to vibrate
      • ear drum vibration = ossicles vibrate and the to oval window
      • pressure waves are produced in cochleas fluid and travel up vestibular channel
      • vibrations cause displacemnts in basilar membrane causing action in cilia - nervious activity
      • higher f act at base of cochlea, higher f act at apex
    • log responses
      • intesnity
        • threshold i = minimum i that humans can hear
      • perceived loudness is not linear- log relationship
      • relative I = LOG10= I1/I0
        • BEL
    • sensitivity
      • hearing deteriorates at a faster rate when exposed to loud sounds
        • 2-5 khz = most sensitive range
      • imbalance of sensitivity = dont hear joints moving ect
      • 30db required to detect 100hz

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