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Module 14: Hearing Vocabulary
14-1: Sound Waves
1) Audition: the sense or act of hearing
2) Frequency: the number of complete wavelengths that pass a point in a given time
3) Pitch: a tone’s experienced highness or lowness; depends on frequency
14-2: The Ear
4) Middle Ear: the chamber between eardrum and cochlea containing three tiny bones
(hammer, anvil, and stirrup) that concentrate the vibrations of the eardrums on the
cochlea’s oval window
5) Cochlea: a coiled, boney, fluid-filled tube in the inner ear through which sound waves
trigger nerve impulses
6) Inner Ear: the innermost part of the ear, containing the cochlea, semicircular canals, and
vestibular sacs
14-3: Perceiving Pitch
7) Place Theory: in hearing, the theory that links the pitch we hear with the place where the
cochlea’s membrane is stimulated
8) Frequency Theory: in hearing, the theory that the rate of nerve impulses traveling up the
auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch
14-5: Hearing Loss
9) Conduction Hearing Loss: hearing loss caused by damage to the mechanical system that
conducts sound waves to the cochlea
10) Sensorineural Hearing Loss: hearing loss caused by damage to the cochlea’s receptor
cells or to the auditory nerves; also called nerve deafness
14-6: Cochlear Implants
11) Cochlear Implant: a device for converting sounds into electrical signals and stimulating
the auditory nerve through electrodes threaded into the cochlea
Module 14: Hearing Vocabulary
14-1: Sound Waves
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Sounds are jostling molecules in the air that bump into each other
Sound waves are special touch sensations sensed through vibrations and air and bone
conduction
The ears turn vibrations of air into never impulses that our brain decodes into sounds
Amplitude determines the volume of sound waves or how loud something is
Lengths of sound waves determine the frequency
Frequency determines pitch
Pitch is measures in decibels
The absolute threshold for hearing is zero decibels (whispers are 20 decibels and a
normal conversation is 60 decibels)
Anything higher than 85 decibels can cause hearing loss
14-2: The Ear
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To be able to hear, sound waves must go through a mechanical chain reaction process to
convert into Neural Activity
1) Sound waves travel through the auditory canal from the outer ear to the eardrum that
vibrates the waves.
2) The waves get transmitted through the middle ear through three tiny bones (hammer,
anvil, and stirrup) to the cochlea in the middle ear.
From there on, the vibrations vibrate the cochlea’s membrane that makes the fluids in its tube
jostle that then ripples the basilar membrane and bends the hair cells that trigger the nerve
fibers (auditory nerve).
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This mechanical reaction causes hair cells to send neural messages (via thalamus) to the
temporal lobe’s auditory cortex.
14-3: Perceiving Pitch
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Two theories have been in place on how we perceive pitch
Place Theory(high pitch): we hear different pitches because different sound waves
trigger activity at different places along the cochlea’s basilar membrane
(the brain can determine a sound’s pitch by recognizing the place on the membrane from
which it receive
Module 14: Hearing Vocabulary
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Frequency Theory(low pitch): the basilar membrane vibrates with incoming sound
waves, triggering neural impulses to the brain at the same rate as the sound waves
Volley Principle: neural calls can alternate firing in rapid succession, in which they can
achieve a combined frequency above 1000 times per second
14-4: Locating Sounds
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The placement of our ears allow us to use stereophonic (3D) hearing
Two ears are helpful because if a sound is going off, the ear closest to the noise receives
the sound slightly sooner than the other one
Sound waves travel 750 miles per hour
Ears are 6-inches apart
Intensity difference and time lag are extremely small
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14-5: Hearing Loss
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Problems with the mechanical system that conducts sound waves to the cochlea cause
conduction hearing loss
Causes: punctured eardrum and inability to vibrate in hammer, anvil, and stirrup
Damage to the cochlea’s hair cell receptors or their associated nerves can cause
sensorineural hearing loss
Causes: occasionally disease, biological changes in heredity, aging, prolonged exposure
to ear-splitting noise or music
Once nerves are destroyed, tissues remain dead
Hearing aids amplify sounds to stimulate neighboring hair cells
Digital hearing aids amplify vibrations for high frequencies and compressing soft sounds
Hair regeneration is possible in sharks and birds. Scientists have found a way to
regenerate hair cells in guinea pigs, but not humans yet.
14-6: Cochlear Implants
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Cochlear implants are used to restore hearing for people with nerve deafness
They translates sounds into electrical signals that convey some information about sound
to the brain