There are several different activities to demonstrate the mechanics of sound. To begin students need to understand that there are several different aspects of a sound and that vibrations create all sounds.
To demonstrate this, a good activity would be to make a singing string.
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1. Loop two feet of thread through two holes of a large button.
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2. Tie the ends together with a knot, one on each side of the button.
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3. Pull the threads so that you have 6 inches of string on each side of the button.
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4. Put your fingers through the loop, and twirl the button around to twist the string.
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5. Pull the string in and out. The button will twirl, and you’ll hear a humming sound as the string vibrates. (Barron’s pg. 67)
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Another demonstration to show vibrations is to put a candle out with sound waves.
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1. In the middle of an oatmeal box lid, cut a hole the size of a penny.
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2. Set the box on its side with the lit candle 4 inches in front of the hole.
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3. Lightly tap the other end of the box. The sound is like a drum.
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4. Be sure to use safety precautions when conducting this experiment.
The candle will flicker and may even go out. The vibrations will be seen through the flame of the candle. (Barron’s pg. 66)
To demonstrate the pitch of a sound wave two simple demonstrations can be used. Play a straw or play on crystal glasses. To play a straw:
1. Fill a bottle of water at different levels.
2. Place a straw in the water, and blow into the other end of the straw.
3. Another variation to this experiment is to simply blow across the top of a soda bottle.
Different pitches will be heard by moving the straw or by adjusting the level of the water. Playing with different crystal glasses will also demonstrate pitch, by running a wet finger around the rim. Again different pitches will be achieved with different levels of water in each crystal glass. (Barron’s pg. 68)
Another fun demonstration to show the mechanics of sound would be to use sound tubes. Sound tubes are spun in a circle and produce different tones. The faster you spin the tubes the higher the frequency of the sound. Students will enjoy exploring with boom whackers. Boom whackers are different length tubes that when hit produce different tones. (Teacher Source, 7/30/03)
Some response questions to follow each activity would be:
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1. Do you think the sounds would change if milk or soda were added to the crystal glasses?
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2. Do you think the string would sing if the button was not round?
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3. What other experiments can you think of to demonstrate the different parts of a sound wave?