Download The Auditory Stimulus

Reading 1
cael assessment practice – academic listening — 19
The Auditory Stimulus
A.
Hearing is a vibratory sense. That is, the
auditory receptors in your ears are sensitive to vibrations of the molecules in the
air around you. These vibrations usually
come in waves, which we call “sound
waves.” Thus the stimulus for hearing (or
“audition”) is usually a vibratory wave of
some kind. (Words such as “audition,”
“audio,” and “auditorium” all come from
the Latin word audire, meaning “to
hear.”)
Imagine yourself seated a couple of feet
above a very quiet pool in a forest. You
take a stone and toss it in the center of the
pond, and what happens? Wave after
wave of ripples circle out from the center
until they strike the edges of the pool. If
you looked closely, you would see that
when one of the waves reached the shore,
it “bounced back” in a kind of watery
echo.
The sound waves that stimulate the auditory receptors in your ear are not very different from the ripples that you create by
dropping the rock in the pond. Whenever
any fairly rigid object is struck forcibly, it
tends to vibrate. As this object vibrates
back and forth, it “makes ripples” in the
molecules of air around it. These “ripples” are really sound waves. That is, they
are waves of energy that pass through the
air just as the ripples pass across the surface of the water when you throw a stone
in the pond. When these sound waves
reach your ear, they set your eardrum to
moving back and forth in rhythm with
the vibrating object. Other parts of your
ear then translate the vibrations of the
Fig. 1: Parts of the Ear
20 — cael assessment test takers’ preparation guide – reading booklet
eardrum into patterns of neural energy
that are sent to your brain so that you can
“hear.”
B.
Your ear has three main divisions: (1) the
outer ear; (2) the middle ear; and (3) the
inner ear.
1. The outer ear is that fleshy flap of skin
and other tissue sticking out from either side of your head. Your outer ear
tends to “catch” sound waves and direct them into a narrow tunnel called
the auditory canal. At the inner end of
this auditory canal is your eardrum, a
thin membrane stretched tautly across
the auditory canal like the skin on a
drum. The eardrum separates your
outer ear from your middle ear.
2. The middle ear is a hollow cavity in
your skull which contains three little
bones called the hammer, the anvil,
and the stirrup (see Figure 1). If you
were to inspect these three little bones
under a microscope, they would look
much like the real-world objects they
are named after. One end of the hammer is connected to the eardrum, so
that when your eardrum moves, it pulls
the hammer back and forth rhythmically.
The hammer transmits this “wave” of
sound energy to the anvil, making the
anvil move back and forth. The anvil
pulls the stirrup back and forth in similar fashion.
Reading 1
The stirrup is connected to another
membrane stretched across an opening
called the oval window. As the stirrup
moves, it forces the membrane on your
oval window to wiggle back and forth
in rhythm too.
The three little bones and the two membranes act as the amplifiers in your own
biological stereo system. By the time
the sound stimulus has reached your
oval window, it is many times louder or
stronger than it was when it first struck
your eardrum.
Your middle ear is like a bubble of air
trapped inside your skull bone. When
you go up in an airplane, the air pressure around you decreases but the
pressure inside your middle ear remains the same. This pressure difference would rupture your eardrum
were it not for the eustachian tube,
which connects your middle ear to
your throat. When you swallow, the
tube opens momentarily, allowing air
to escape from your middle ear. Each
time your ears “pop” on a plane ride,
your eustachian tube has opened
briefly to reduce the pressure difference between air in your middle ear
and the air outside.
3. The oval window separates the middle
ear from the inner ear. Your inner ear
is a fluid filled cavity that runs through
your skull bone like a tunnel coiling
through a mountain. This inner ear of
yours has two main parts: (1) the
cochlea; and (2) the motion detectors
Reading 1
(the saccule, the utricle, and the semicircular canals).
The cochlea gets its name from the Latin
word for “snail shell,” which is just what
your cochlea looks like. Your auditory receptors are hair cells which are part of the
organ of Corti inside your cochlea. Input
messages from the hair cells pass along the
auditory nerve to the lower centers of the
brain, which relay them up to the temporal lobe of your cortex. Generally speaking, you are not consciously aware of hearing anything until the auditory message
reaches your cortex.
C.
Sound waves have two important physical
aspects: Their frequency and their amplitude.
The frequency of a musical tone is related
to how high or low the tone sounds to
your ear. Put more precisely, the psychological pitch of a tone is primarily determined by the physical frequency of the
sound wave.
The amplitude of a musical tone is related
to how loud or soft the tone sounds to
you. Put more precisely, the subjective
loudness of a tone is primarily determined
by the objective amplitude of the sound.
“Pitch” and “loudness” are terms that describe psychological attributes of the subjective experience of hearing. “Frequency” and “amplitude” are terms that describe the physical characteristics of the
auditory stimulus.
cael assessment practice – academic listening — 21
Definitions
Outer ear. The fleshy outer part of the ear. Also
called the auricle (AW-rick-cull), the pinna (PINnah), or the auditory meatus (me-ATE-us). The
outer ear catches sound waves and reflects them
into the auditory canal.
Auditory canal (AW-dit-tor-ee). The hollow tube
running from the outer to the middle ear.
Middle ear. Contains the hammer, anvil, and stirrup. Lies between the eardrum and the oval window.
Hammer, anvil, and stirrup (STIR-up). Three
small, connected bones in your middle ear that
make sounds louder.
Oval window. The thin membrane lying between
your middle and inner ears. The stirrup is connected to one side of the oval window, the basilar
membrane (BASS-sih-lar) which supports the organ of Corti is connected to the other.
Eustachian tube (you-STAY-shun). A narrow
canal connecting the middle ear to the throat.
Opens briefly when you swallow to allow the air
pressure in the middle ear to equalize with the
pressure of outside air.
Inner ear. A fluid-filled “worm hole” in your
skull that contains both the motion detectors (the
saccule, utricle, and semi-circular canals) and your
receptor neurons for hearing.
Cochlea (COCK-lee-uh). The snail-shaped portion of your inner ear that contains the basilar
membrane.
Organ of Corti (KOR-tie). A highly complex
structure lying on the basilar membrane that contains the sensory receptor cells for hearing.
Frequency. In auditory terms, the number of
times a sound source vibrates each second. The
frequency of a musical tone is measured in Hertz.
Amplitude (AM-plee-tood). From the Latin
word meaning “muchness.” We get our word
“ample” from the same Latin source. Amplitude is
the amount of sound present, or the strength of a
musical tone. Literally, the “height” of a sound
wave.
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Reading 1
D.
If you drop a stone in a deep pond, you
set up just one big wave that moves out
from the point at which the stone hits the
water. But if you drop several pebbles in,
one after the other, you set up a series of
waves. If you dropped in 10 pebbles each
second, you would set up 10 waves a second (under perfect conditions). The frequency of the waves would then be 10 per
second.
When you pluck a string on a guitar, you
are doing much the same thing as dropping a rock in a pond. For the string creates sound waves that have exactly the
same frequency as the number of vibrations that the string makes per second.
Your ear detects these sound waves, and
your brain turns them into musical tones.
The faster a particular string vibrates, the
more “ waves per second” it creates—and
the higher the pitch of the tone will seem
to be when you hear it.
If you plucked the “A” string on a guitar,
it would vibrate 440 times per second.
This number is called the frequency of the
musical tone “A.” In technical terms, we
would say that this tone has a frequency
of 440 “cycles per second,” or 440 Hertz
(440 Hz). In general, the thinner and
shorter a string is, the higher the frequency at which it vibrates—and the higher
the pitch of the tone that it makes.
E.
The loudness of a tone is determined primarily by the tone’s amplitude, not by its
frequency. If you happen to pluck the
Fig. 2: A sound wave “cycle” or
“Hertz” is measured from peak to peak.
“A” string of the guitar very gently, it vibrates 440 times per second. But if you
plucked the string as hard as you could, it
would still vibrate at about 440 Hz. If it
didn’t, you wouldn’t hear the note as being an “A.”
But surely something different happens,
for the more energetically you pluck a
string, the louder the note sounds. The
answer is that the string moves further up
and down during each vibration—but it
still vibrates at about 440 times per second
(see Fig. 2). In similar fashion, if you gently drop 10 pebbles per second into a
pond, you create 10 very small waves. But
if you throw 10 pebbles per second into a
pond as hard as you can, you create 10
very large waves. In either case, however,
there are still just 10 waves per second.
Reading 1
cael assessment practice – academic listening — 23
In technical terms, the “bigger the wave,”
the greater its amplitude. And the greater
the amplitude that a sound wave has, the
louder it will sound to your ear.
F.
What kinds of musical tones can your ear
hear?
Your range of hearing is, roughly speaking, from 20 Hz to about 20,000 Hz. But
you are not equally sensitive to all frequencies within this range. Your hearing
is best from about 400 to 4,000 Hz. Human conversation ranges between 200 and
800 Hz. The lowest tone a bass singer can
produce is about 100 Hz, while the highest tone most sopranos can produce is
Fig. 3: A vibrating guitar string.
about 1,000 Hz. Thus your ear is “tuned”
to listen to other people speak (and sing).
There seems to be a general rule that
holds across animal species: The smaller
the cochlea, the higher the animal’s range
of hearing is likely to be. The dog can hear
notes at least as high as 25,000 Hz, while
the bat is sensitive to tones as high as
100,000 Hz. Elephants, on the other
hand, probably have a hearing range that
cuts off at about 7,000 Hz.
Definitions
Hertz (hurts). The frequency of any wave, such as
a sound wave. Used to be called “cycles per second,” or CPS. Named for the German scientist
Heinrich Hertz who made the first definitive
studies of energy waves.
Bone deafness. A form of hearing loss caused by
damage to the three bones of the middle ear. Often
occurs naturally in old age. Usually can be helped
either by use of a hearing aid or, occasionally, by
surgery.
Nerve deafness. A form of hearing loss caused by
damage to the hearing receptors or to the auditory nerve. Nerve deafness can seldom be helped either by surgery or by use of a hearing aid.
Spectrum (SPECK-trum). From the Latin word
meaning “to look,” from which we also get the
words “specter” (ghost) and “spectacle.” The
word “spectrum” means a set or array of related
objects or events, usually a set of sights or sounds.
Paranoia (pair-ah-NOI-ya). A severe type of
mental disorder characterized by delusions of
grandeur and suspicions that people are whispering about you or trying to control your behaviour.
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G.
Reading 1
What difference would it make to your
life if you became deaf?
spread, however, you might become totally deaf for all frequencies. Nerve deafness
can seldom be corrected either by surgery
or by a hearing aid.
Hearing is the major channel for informal
social communication. Our customs, social graces, and moral beliefs are still
passed down from one generation to another primarily by word of mouth rather
than in writing. And most of us (textbook
writers included!) prefer the informal
transmission of knowledge that comes
from talking to the formality of the written word.
There are two major causes for nerve
deafness—disease, and exposure to extremely loud sounds. The jet engines on
modern airplanes create ear-splitting
sounds, which is why people who work
around jets wear protective earphones.
The sound levels in many factories can
cause damage too if the workers are exposed to the noise for too long a time.
H.
When people grow older, the three small
bones in the middle ear often become
brittle and thus do not work properly.
Since the hammer, anvil, and stirrup serve
to amplify the sound waves as they come
into the ear, you usually become deaf
when these bones malfunction. This type
of bone deafness can usually be corrected
if you are fitted for a hearing aid, a device
that acts like a miniature hi-fi set and
“turns up the volume” electronically (see
Fig. 3). Some severe types of bone deafness can be corrected by surgery.
Many types of infection can attack the
hair cells on the organ of Corti. If your
receptor cells were permanently damaged
for any reason, you would suffer from
nerve deafness. If only a small section of
your basilar membrane were affected, you
would lose the ability to hear just high
notes, or low notes, or even notes in the
middle of the auditory spectrum. If the
damage to your nerve cells was wide-
Reading 1
I.
According to Philip Zimbardo, older individuals who slowly lose their hearing
may be reluctant to admit their growing
deafness. For to do so, Zimbardo says,
would be to admit that they are “growing
old.” Thus many older people with hearing losses tend to blame their hearing
problems on the behaviour of others
rather than on their own faulty ears. This
“blaming behaviour” often takes the form
of a mild paranoia, in which older people
grow highly suspicious that others are
whispering about them behind their back.
In the June 26, 1981 issue of Science, Zimbardo and two of his associates report the
results of a study they performed on “experimental deafness” at Stanford. The
psychologists began by hypnotizing some
cael assessment practice – academic listening — 25
reversible. Zimbardo and his colleagues
then asked the temporarily hard-of-hearing subjects to work together in discussion groups with normal subjects. The
tasks the discussion groups had to accomplish were, for the most part, the sort of
“problem-solving exercises” that psychologists often ask subjects to engage in.
The experimental subjects were given
personality tests both before and after the
problem-solving sessions.
Zimbardo and his colleagues report that
most of the temporarily deaf students
showed marked signs of mild paranoia.
That is, the subjects became convinced
that the other members of their discussion
groups were “talking ill” of them, or were
trying to do them harm. They also became more hostile, confused, agitated, irritable, and less creative. Zimbardo believes that the tendency to blame other
people for one’s own faults may explain
many personality disorders, including
some types of paranoia.
J.
Many older people maintain good hearing.
Those who don’t often become paranoid and
suspicious.
of their subjects and telling them that they
would have severe difficulties hearing
other people talk. This sort of temporary
hearing loss under hypnosis is completely
If you are telling someone a story or teaching someone a lesson, you typically will
watch your listener’s face. And the person
who is listening will usually respond with
a smile or a nod of the head to indicate understanding or agreement with what you
have said. This feedback from your listener is of critical importance in shaping your
own verbal behaviour. For communication is best when it is a two-way street.
You give out a message. It is received by a
listener who, in turn, sends you back a
Reading 2
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message evaluating or responding to what
you have said.
they simply do not know what their own
voice sounds like.
Learning to sing, dance,
play the guitar, or drive
a car—all these complex
motor tasks require
feedback. Children who
are born deaf—or partially deaf—have trouble learning to talk because they cannot hear
what noises their voices
are making. Without
the auditory feedback
Some kinds of deafness from their vocal cords,
children can never learn
can be helped with
hearing aids.
to shape their spoken
words properly, because
Until scientists discovered how necessary
some kind of feedback is in learning to
talk, we often thought that partially deaf
children were dumb or stupid. Occasionally we mistakenly confined these children to homes for the mentally retarded—although many of them had very
high intelligences. Fortunately, now that
hearing tests for young children are much
more common than they used to be, we
are less likely to confuse partial deafness
with mental retardation.
A S S E S S M E N T