Download Chapter 4 Section 3

Ch. 4 S. 3
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Chapter 4 Section 3
Hearing
Obj: Describe how the _______ perceives ________________
Sound travels through the air in _________________. It is caused by changes in air pressure that
result from _____________________. Anything that makes a sound causes vibrations. Each of
these vibrations is called a cycle or a sound wave. Every _____________ has its own pitch and
loudness.
Pitch
Sound waves can be very fast, occurring many times per second. The _______________ of a soundhow high or low the sound is-depends on its frequency, or the number of cycles per second. The
more cycles per second, the higher the pitch of a sound.
Women’s voices usually have a higher pitch than those of men because women’s ______________
cords tend to be shorter and therefore ________________ at a greater frequency.
The human ______ can hear sound waves that vary from 20 to 20,000 cycles per second. Many
animals, including dogs and ___________________, hear sounds well beyond 20,000 cycles per
second. Although we cannot hear them, the sounds emitted by dolphins help them locate others.
The sound ________________ echo back from fish and other objects.
Loudness
What is the _______________ sound you can hear? What is the loudest? The loudness of a sound is
determined by the height, or amplitude, of sound waves. The higher the _________________ of
the wave, the louder the sound. The loudness of a sound is measured in ________________, a
unit that is abbreviated dB. Zero dB is considered the threshold of hearing. Zero dB is about as
loud as the ticking of a watch 20 feet away in a very quiet room.
The Ear
Just as the eye is the human instrument for _________________, the ear is the instrument for
sensing all the sounds around us. In fact, the ear is shaped to capture sound waves, to
__________________ with them, and to transmit sound to the brain. What we normally think of as
the ear is actually the outer ear. We also have a middle ear and an ____________ ear.
The ____________________ is the gateway from the outer ear to the middle ear. It is a thin
_______________ that vibrates when sound waves strike it. As it vibrates, it transmits the sound to
three small bones in the middle ear: the hammer, the anvil, and the _______________. (The
stirrup is the smallest bone in the human body). These bones then also begin to vibrate and
transmit sound to the inner ear.
The inner ear consists of the cochlea. The word cochlea comes from the Greek word for “snail”. The
__________________ is a bony tube that contains fluids as well as neurons that move in response
to the vibrations of the fluids. The movement generates neural impulses that are transmitted to the
brain via the _______________ nerve. Within the brain, auditory input is projected onto the
hearing areas of the ______________ cortex.
Deafness
Not everyone perceives ______________. About 2 million Americans are _________. Deafness may
be __________________ or caused by disease, injury, or old age.
• ____________________ Deafness – If we see an older person with a hearing ________, we can
assume that he or she is probably suffering from conductive deafness. Conductive deafness
occurs because of _______________ to the middle ear. Since this part of the ear amplifies sounds,
damage to it prevents people from hearing sounds that are not loud enough. Fortunately, people
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with conductive deafness are often helped by hearing aids. These aids provide the
_________________ that the middle ear does not.
• __________________________ Deafness – Many people do not perceive sounds of certain
________________. This is a sign of sensorineural deafness. Sensorineural deafness is usually
caused by damage to the inner ear. Most often, the neurons in the cochlea are destroyed.
Sometimes sensorineural deafness is due to damage to the auditory nerve, either through
_______________ or through prolonged exposure to very loud sounds.
Have you ever attended a high-volume rock concert and left with a ringing sensation in your ears?
This may have meant that ___________________ had been destroyed in your ears. The same
thing can happen to workers who operate certain drilling equipment or drive loud vehicles. The next
time you are exposed to loud ___________, remember to cover your ears.
Devices called experimental cochlear implants, or “artificial ears,” contain microphones that sense
sounds and electronic equipment that stimulates the auditory nerve directly. However, if the
auditory nerve itself is damaged, a cochlear ____________ cannot help.
• Deafness in the World ___________ – In recent years, people who are ________ have been able
to come more into the mainstream of sensory experience as a result of their own efforts, the efforts
of others, and new technology. Heather Whitestone became Miss ___________________ in 1995.
__________________ are often on hand to translate speeches into languages (such as American
Sign Language) used by members of the audience who are hearing impaired. More and more
schools are offering courses in American Sign Language. Many television shows are now “closed
captioned,” which means that special ________________ make captions of dialogue visible on the
screen. And, as you have just read, scientists are always trying to find new ways to counteract
______________ inside the ear.