Hearing

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Hearing

• As with the eye, the ear receives waves, this
  time of sounds.
• Length of wave pitch
• height of wave (amplitude) volume

2
Volume

• Volume measured in decibels.
• Every 10 point increase equals a 10 times rise in
  level.
• Frequent exposure to 85 possible deafness
• A busy street corner
• 85 decibels is a trillion times louder than the
  lowest threshold for hearing sound.

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The Ear

• Outer ear funnels waves into auditory canal to
  the tympanic membrane
• Tympanic membrane Eardrum tight vibrating
  membrane
• Tympanic membrane attached to bones of the middle
  ear called ossicles
• the hammer, anvil, and stirrup piston movement
• The bones are attached to the Cochlea in the
  inner ear through the oval window.
• The Cochlea is to hearing what the retina is to
  seeing the receptor.

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Pinna

• External visible flap of skin and cartilage

5
Auditory Canal

• Part of outer ear along with pinna, leads to
  tympanic membrane

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Tympanic Membrane

• Also called eardrum
• Separates outer ear from middle ear and vibrates
  with reception of sound

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Ossicles

• Three bones in middle ear (malleus/incus/stapes
  or hammer/anvil/stirrup)
• Set in motion by eardrum that transmit sound
  vibrations to the cochlea

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Cochlea

• Basilar membrane subject to pressure changes in
  cochlear fluid
• Contains the organ of Corti an organ that
  contains auditory sensory cells (hair)
• Hair Cells organ of Corti deflected by fluid
  movement trigger neural impulses to the brain via
  auditory nerve

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Basilar Membrane Amber fields of grain
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The Cochlea how it works

• When the bones of the middle ear shake (piston)
  the cochleas oval window, it makes the liquid
  inside ripple which, in turn, vibrates the hairs
  embedded in the basilar membrane.
• This vibrating creates the action potential.

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Hair cells of inner ear, can be damaged by age
and loud noise, particularly bass sounds.
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Pitch

• Place theory high pitches are created by where
  on the basilar membrane the liquid vibrates the
  hairs.
• The brain reads the place and makes you hear the
  corresponding pitch. (high pitches)

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Pitch

• Frequency Theory brain reads amount of times
  per second the hair vibrates and interprets to
  determine low or high pitches.

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Sound location

• Your brain uses a combination of visual cues and
  sound cues to determine sound location. (parallel
  processing).
• The sound cues are the level of amplitude that
  each ear receives. The visual cues can fool you,
  like with a ventriloquists dummy. (dichotic
  listening test)

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Deafness

• Conduction Deafness Caused by damage to the ear
  drum or middle ear bones.
• Hearing aids can help by increasing the amount of
  sound waves to the cochlea.
• Sensorineural Deafness (Nerve Deafness) caused
  by damage to the hairs by repeated exposure to
  loud noises or disease.
• Rarely helped by hearing aids. Possible in the
  future by cochlea transplants.
• http//www.youtube.com/watch?vZT7sxr9t3Qgfeature
  related

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Perception and Attention Change

• Incoming information more important due to lack
  of auditory input
• Deaf people tend to take in visual inputs more
  than most (i.e. ability to read lips)

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Hearing loss

• Tends to be in the higher pitch ranges. Makes it
  hard to pick out foreground from background.
  Higher frequency hairs are at beginning of
  cochlea
• If cant talk over sound.
• If others can hear your IPOD
• If ringing in the ears.

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Body Senses

• Vestibular sense fluid filled, semi circular
  canals in inner ear that monitor head position,
  thus body position.
• Kinesthesis Sense of body and body part
  position and movement are located in the joints
  muscles and tendons. If not you would be a rag
  doll.

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Hearing Test

• http//www.freemosquitoringtones.org/hearing_test/