From Vibration To Sound
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Persons, Pamela Walt Disney Magnet School
1. To identify the parts of a sound wave.
2. To distinguish between a transverse wave and a compressional wave.
3. To describe how musical instruments produce sounds.
An overhead projector, plastic dish, glass, corks or stoppers of
different sizes, tuning forks, rope, slinky, tin cans, string, paper
clips, test tubes, test tube rack, student-made instruments, rubber
tubing, 6 V cell and connecting wire, a jar of vacuum grease, electric
vacuum pump and stand, bell jar and electric bell.
1. Discuss that sounds we hear are vibrations of molecules in air and
other materials. They carry energy in waves that can be reflected,
absorbed and transmitted like light waves, but cannot travel like
light in a vacuum.
2. Place a large square, clear glass or plastic dish on an overhead
projector. Fill the dish one third full of water. Drop corks or
stoppers of different sizes into the center of the water and project
the resulting wave motion onto a screen. Discuss what caused the waves
and their characteristics. Now strike a tuning fork and touch the stem
to the surface of the water. Observe the wave pattern produced.
Discuss the cause of waves.
3. Tie one end of a rope to a doorknob. Produce transverse waves
along the rope by shaking one end.
4. Use a long slinky-type spring to illustrate longitudinal and
5. Point out that wavelength can be measured from crest to crest,
trough to trough, or any other two corresponding points.
6. Diagram a wave and label its wavelength and amplitude.
7. Relate sound to mechanical vibrations of all sorts. For example, a
drum beat, the snap of a breaking stick, a truck rumbling by on a
street. Discuss the vibration one can feel in the speaker of a stereo.
8. Explain the scientific meaning of "tuning in" a certain radio
station (the adjusting of the circuit in a radio so that the circuit
resonates electrically at the broadcasting frequency of the radio
9. Use student-made instruments to illustrate volume and pitch (one-
string guitar, earharp, sandpaper blocks, paper tube kazoo, wind
chimes, wood block tambourine, tongue depressor finger piano, garden
hose recorder, etc.)
10. (IF AVAILABLE) Set up the demonstration of a bell in a vacuum.
With the bell ringing, pump the air out of the bell jar, and then
allow the air to fill the system again. Discuss why the sound of the
bell gets fainter until no sound can be heard.
11. Prepare "learning stations" with independent activities related to
the production of sound. For example:
A> Waves in a Coil Spring (To demonstrate a compressional wave)
B> Talking Through A String Telephone (To hear the transmission of
C> Tuning Fork Sounds (To discover how pitch is related to the
frequency of sound waves)
D> Test Tube Organ (To determine how the length of an air column
affects the frequency of the sound)
12. As enrichment activities students could research the following:
1). Seismic waves transmit the energy of an earthquake. Research
earthquakes to determine the types of waves made.
2). Traditionally, soldiers break step when crossing a bridge. In
the 1800s a group of soldiers crossing a bridge in step set up
a vibrational pattern that caused the collapse of the bridge.
Research this incidental bit of history under the topic of
bridges or vibrations.