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Good vibrations! |
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Informations |
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Project:
Good vibrations! |
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Developed By:
Frédérick Moreau |
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Type of Project:
Experiment |
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Category:
Physical science |
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Class:
Junior |
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Age of Participant:
13 |
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School:
Séminaire de Chicoutimi |
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Teacher:
Carol Tremblay |
Project presented at the 1998 Saguenay—Lac-Saint-Jean regional final
of the Bell Science Fair
Selected for the 1998 Quebec final (Montreal) of the Bell Super Science
Fair
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Introduction |
Sound plays an important role in our lives. Our
sense of hearing—which decodes sound—is very valuable. Imagine
life without sound. There would be no music or singing! Since I was very
young, I have always wondered how sound travels. For my Science Fair
project, I conducted a few experiments in order to validate the fact
that “sound is a vibration of air.”
How do we capture sound?
Let’s begin by briefly discussing the ear. The ear is a bit like
a machine for detecting sound. It is divided into three parts: the outer
ear, the middle ear and the inner ear. The outer ear consists of the
ear flap and most of the ear’s auditory canal. The middle ear consists
of the remaining portion of the auditory canal—the tympanic membrane
or eardrum—as well as the hammer, the anvil, the stirrup and part
of the semicircular canals. Finally, the inner ear is made up of the
Eustachian tube, the cochlea and the auditory nerve.
Sound is a vibration
Sound is a vibration of air that causes the eardrum to oscillate. Two
effective methods are often used to illustrate this hypothesis: echoes
and ultrasound waves. If sound weren’t a vibration of air, there
simply wouldn’t be such a thing as an echo. Why? Because it is
the vibrating nature of sound that allows it to travel through the air, “bounce
off” objects and return to your ear in the form of an echo. Ultrasound
waves are high-pitched sounds produced by certain animals—like
bats—to locate their prey or other objects. The animal produces
ultrasound signals, which travel through the air, bounce off a tree,
for example, and return to the animal. The time the signal takes to return
to the animal enables it to determine how far away the tree is. If there
is no object in its path (which is quite unusual in a world like ours)
the sound does not return. Once again, ultrasound signals can be detected
because sound is a vibration of air. Pretty ingenious, isn’t it?
It is important to mention that sound can travel anywhere: in liquids,
solids and gases (e.g. air). Sound also comes in various forms: vibrations
in air or waves in liquids and solids. Sound travels fastest in solids.
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Experiment 1:
“Seeing sound” |
I was sure that talking into a tin can would enable me to “see” sound.
I took a tin can and removed both ends. I then took a balloon, cut off
the opening and stretched it over one end of the tin can. After that,
I glued a small mirror to the stretched-out balloon and placed a flashlight
in such a way that the light would be reflected by the mirror onto a
white wall. When I spoke into the tin can, I was able to see sound!
How was I able to see sound? Since sound is a vibration, by making sounds
into the tin can covered at one end by the outstretched balloon, I caused
the balloon surface to vibrate. The balloon, in turn, caused the mirror
to vibrate and, consequently, the reflection of the light moved on the
wall, enabling me to see sound.
Interesting fact: The more low-pitched the sound, the more the vibration
is visible because the low-pitched sound makes the balloon vibrate more.
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Experiment 2:
“Feeling sound move” |
My aim here was to “feel” sound. To do so, I cut a piece
of aluminum foil large enough to cover my entire hand. I then placed
the aluminum foil on my hand and made a “hoooooo” sound.
As a result, the aluminum foil vibrated.
The aluminum vibrates because the sound travels through the air and the
air changes, depending on the force and pitch of the sound. This also
proves that sound is a vibration.
I can therefore say that I felt sound.
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Experiment 3:
“Transmitting sound vibrations” |
This time, I took a toilet paper roll. Using a piece of cardboard, I
cut out two circles large enough to cover the ends of the roll. I made
a small hole in one of the circles and attached the circles to the ends
of the roll.
I lit a candle approximately 10 cm from the end with the pierced hole.
I flicked the other end with my finger. As a result, the candle flame
flickered and even went out occasionally.
Why did the flame flicker or go out? This phenomenon is the result of
sound waves produced by the flicking sound, which then travelled through
the air. This wave motion caused the flame to flicker or go out.
A few historical notes
Sound is a vibration that travels through the air; sound cannot travel
in a vacuum. In 1660, an English scientist by the name of Robert Boyle
demonstrated this by placing an alarm clock in a glass container from
which the air had been removed. Failing to hear his alarm clock go off
at the usual time, Boyle slept in and was late for work. He had proven
that sound could not travel in a vacuum.
Why is there no sound in space? To find out, we would need to know more
about the composition of gases in space.
Until 1877, it was impossible to record sound. That year, however, Thomas
Edison came up with his new invention—the phonograph—a device
used to record sound vibrations.
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Conclusion |
This Science Fair project is a study carried out by a Secondary II student
to understand how sound travels. |
© 2002, Conseil de développement du loisir scientifique (CDLS). This
document is distributed by the Conseil de développement du loisir scientifique.
For more information, visit our Web site at www.cdls.qc.ca. |
The opinions expressed
in this section are those of the authors and do not necessarily
reflect the opinions of Merck Frosst or its employees. |
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