HearingHearingChapter 6, Lecture 3Chapter 6, Lecture 3

“From vibrating air to moving piston to fluidwaves 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)

The Ear Dr. Fred H

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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.

CochleaCochlea: 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

70dB

120dB

Richard K

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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 differences2. 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?Can we practice this in class?

Hearing Loss

How might someone How might someone develop each of these?develop each of these?

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.

Let’s read more about hearing Let’s read more about hearing loss…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 loudmusic, a carpeted restaurant, a chair away from the airconditioning.

• 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, ithelps to see your mouth. And don’t conclude that we are rude ifwe look at your mouth rather than your eyes.

• Speak slowly. Don’t holler, but enunciate each word withpauses 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 usingdifferent words to express the same thought. Change “Do youwant something from the store?” to “Can I get you something atSafeway?”

• Create a context. Help us to know the subject. Have a printedagenda for meetings, use visual aids. Caller I.D. is a blessing forus.

• Ask us if we have heard. Remember, we don’t like to seem ineptor to embarrass both of us by volunteering what we did not hear.

HomeworkRead p.252-263

“People who lose one channel of sensation doseem to compensate with a slight enhancementof their other sensory abilities.”

- David Myers