Hearing
Chapter 6, Lecture 3
“From vibrating air to moving piston to fluid
waves to electrical impulses to the brain: Voila!
We hear.”
- David Myers
Hearing
The Stimulus Input: Sound Waves
Sound waves are compressing and
expanding air molecules.
Sound Characteristics
1. Frequency (pitch)
2. Intensity (loudness)
Dr. Fred Hossler/ Visuals Unlimited
The Ear
The Ear
Outer Ear: Collects and sends sounds to the
eardrum (the pinna).
Middle Ear: Chamber between eardrum and
cochlea containing three tiny bones (hammer,
anvil, stirrup) that concentrate the vibrations
of the eardrum on the cochlea’s oval window.
Inner Ear: Innermost part of the ear,
containing the cochlea, semicircular canals,
and vestibular sacs.
Cochlea
Cochlea: Coiled, bony, fluid-filled tube in the inner ear
that transforms sound vibrations to auditory signals.
Intensity (Loudness)
Intensity
(Loudness): Amount
of energy in a wave,
determined by the
amplitude, relates to
the perceived
loudness.
Loudness of Sound
Richard Kaylin/ Stone/ Getty Images
120dB
70dB
Frequency (Pitch)
Frequency (pitch):
The dimension of
frequency
determined by the
wavelength of
sound.
Wavelength: The
distance from the
peak of one wave to
the peak of the next.
Perceiving Pitch
Place Theory: the theory that links the pitch we hear
with the place where the cochlea’s membrane is
stimulated (good for determining high pitches).
Frequency Theory: the theory that the rate of nerve
impulses traveling up the auditory nerve matches the
frequency of a tone (good for determining low
pitches).
Localization of Sounds
Because we have two ears, sounds that reach
one ear faster and with greater intensity than the
other ear cause us to localize the sound.
Localization of Sound
1. Intensity differences
2. Time differences
Time differences as small as 1/100,000 of a second
can cause us to localize sound. The head acts as a
“shadow” or partial sound barrier.
Can we practice this in class?
Hearing Loss
Conduction Hearing Loss: caused by damage to the
mechanical system that conducts sound waves to the
cochlea
Sensorineural Hearing Loss: caused by damage to
the cochlea’s receptor cells or to the auditory nerves;
also called nerve deafness.
How might someone develop
each of these?
Let’s read more about hearing loss…
From A Quiet World by David Myers
Myers passes along these specific tips for friends,
colleagues, and family members of the hearing impaired:
• Invite us to a quiet place, for example, a room without loud
music, a carpeted restaurant, a chair away from the air
conditioning.
• Capture our attention. If we are reading or watching television,
make certain we’re looking at you.
• Face the light and face us. Since we all do some lipreading, it
helps to see your mouth. And don’t conclude that we are rude if
we look at your mouth rather than your eyes.
• Speak slowly. Don’t holler, but enunciate each word with
pauses between phrases and sentences.
From A Quiet World by David Myers
Myers passes along these specific tips for friends,
colleagues, and family members of the hearing impaired:
• Rephrase. If we don’t seem to hear it, restate it. Try using
different words to express the same thought. Change “Do you
want something from the store?” to “Can I get you something at
Safeway?”
• Create a context. Help us to know the subject. Have a printed
agenda for meetings, use visual aids. Caller I.D. is a blessing for
us.
• Ask us if we have heard. Remember, we don’t like to seem inept
or to embarrass both of us by volunteering what we did not hear.
Homework
Read p.252-263
“People who lose one channel of sensation do
seem to compensate with a slight enhancement
of their other sensory abilities.”
- David Myers