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Hearing Test
• http://www.freemosquitoringtones.org/hearing_test/
Audition: Hearing
• As with the eye, the ear receives waves, this time of sounds.
• Length of wave = pitch
• height of wave (amplitude) = volume
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.
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.
Tympanic Membrane
• Also called eardrum• Separates outer ear from middle ear and
vibrates with reception of sound
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
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
The Cochlea – how it works• When the bones of the middle ear
shake (piston) the cochlea’s 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.
Pitch Theories• 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)
Pitch theories cont’d
• Frequency Theory: brain reads amount of times per second the hair vibrates and interprets to determine low or high pitches.
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 ventriloquist’s dummy. (dichotic listening test)
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?v
=ZT7sxr9t3Qg&feature=related
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)
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 can’t talk over sound.• If others can hear your IPOD• If ringing in the ears.