Hearing (Audition) Audition: the sense or act of hearing. Sound
waves result from mechanical vibration of molecules from a sound
source (e.g. instrument or voice).
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Hearing (Audition) Amplitude: The height of the sound wave the
determines the loudness. The bigger the amplitude, the louder the
sound.
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Hearing (Audition) Frequency: the number of complete
wavelengths that pass a point in a given amount of time.
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Hearing (Audition) Pitch: the highness or lowness of a sound.
Shorter Wavelength Higher Pitch Higher Frequency = = Longer
Wavelength Lower Pitch Lower Frequency = =
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Hearing (Audition) We are most sensitive to frequencies that
correspond to the range of human voices.
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Hearing (Audition) Decibels measuring unit for sound energy.
Prolonged exposure above 85 decibels produces hearing loss.
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The Ear Outer Ear: visible part of the ear; channels the sound
waves through the auditory canal to the eardrum. Middle Ear: the
chamber between the eardrum and cochlea. Inner Ear: innermost part
of the ear, containing the cochlea, semicircular canals, and
vestibular sacs.
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Middle Ear Hammer, anvil, and stirrup: a piston in the middle
ear made up of containing three tiny bones that concentrate the
vibrations of the eardrum on the cochleas oval window (membrane).
Eardrum: a tight membrane that vibrates with the waves.
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The Inner Ear Cochlea: a coiled, bony fluid-filled tube in the
inner ear through which sound waves trigger nerve impulses. (Looks
like a snail!) The vibrations on the cochleas oval window cause
vibrations that move the fluid in the tube.
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The Inner Ear Basilar membrane: lined with hair cells that are
bent by the vibrations from sounds and triggers impulses in the
adjacent nerve fibers that converge to form the auditory nerve. The
neural messages travel via the thalamus to the temporal lobes
auditory cortex and we hear!
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The Ear Semicircular canals: three fluid- filled bony channels
in the inner ear. They provide information about orientation to the
brain to help maintain balance. Auditory nerve: axons of neurons in
the cochlea converge transmitting sound messages through the
medulla, pons, and thalamus to the auditory cortex of the temporal
lobe.
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Human Ear Video
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The Ear Loud sounds damage the hair cells which accounts for
most hearing loss. We detect sound by the number of hair cells
activated.
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The Ear
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Determining Pitch How can you discriminate small differences in
sound frequency or pitch? Place theory: we hear different pitches
because different sound waves trigger activity at different places
along the cochleas basilar membrane. Works best with high pitched
sounds.
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Determining Pitch Waves that peak near the close end are
perceived as high-pitched. Waves that peak near the far end are
interpreted as low-pitched.
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Determining Pitch Frequency theory: we sense pitch by the
basilar membrane vibrating at the same rate as the sound. Frequency
theory explains how you hear low-pitched tones. Place theory
explains how we sense high pitches and frequency theory explains
how we sense low pitches.
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Locating Sounds Sound localization: the process by which you
determine the location of a sound. With ears on both sides of our
head, you can locate a sound source. The side closest to the source
of the sound hears it louder.
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Locating Sounds Using parallel processing, your brain processes
both intensity and timing differences to determine where the sound
is. It is hardest to locate a sound directly in front, behind,
above, or below you because the sound hits both ears at the same
time.
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Hearing Loss Conduction hearing loss: loss of hearing that
results when the eardrum is punctured or any of the tiny bones in
middle ear lose their ability to vibrate. A hearing aid may restore
hearing. Nerve (sensorineural) deafness: loss of hearing that
results from damage to the cochlea, hair cells, or auditory
neurons. Cochlear implants may restore some hearing.