Lesson I: Making Sound Waves Visible
Materials Needed
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Bowl or Cake pan
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Water
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Rubber Mallet
Procedures
(1) Strike the tuning fork against a rubber mallet and hold it in the air. Observe what happens to the tuning fork.
(2) Fill the bowl almost to the top with water.
(3) Strike the tuning fork against the mallet once again and stick it into the bowl of water. Observe what happens to the water in the bowl.
Conclusion
What happened when you struck the tuning fork against the mallet? What happened when you struck the tuning fork against the mallet and placed it in the bowl of water?
Explanation
Once the mallet is struck by the tuning fork it vibrates and produces sound. The vibration coming from the tuning fork causes the water to move out in wave formation.
Lesson II: Frequencies of Different Sounds
Materials Needed
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Wood ruler
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Plastic ruler
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Large rubber band
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Small rubber band
Procedures
(1) Place the metal ruler on your desk so that about half of it is sticking out from the edge of your desk.
(2) While your partner holds the ruler in place, press down firmly on the edge of the ruler and release the ruler. Observe how fast the ruler vibrates and the sound it makes.
(3) Repeat steps 1 and 2, with about three-fourths of the ruler is sticking out from the edge of the desk.
(4) Using the ruler made from wood, repeat steps 1, 2, and 3.
(5) Using the ruler made from plastic, repeat steps 1, 2, and 3.
Conclusion
Did you notice a difference in the sound and how fast the rulers vibrated (frequency) when you had it half and three-fourths of it hanging off the side of your desk? Explain. Were there any differences between how fast the rulers vibrated (frequency) and sound of the different rulers? Explain. What did you find out from this experiment?
Explanation
Vibrations caused the sounds produced by the rulers. The speed at which the vibrations occurred determines its frequency. The length of a vibrating object affects it pitch. The materials an object is made of affects its frequency.
Lesson III: Making Musical Sounds by Changing Pitch
Materials Needed
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Eight empty plastic or glass bottles that are the same size
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Water
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Pencil
Procedures
(1) Arrange the bottles in a row and fill the first one close to the top with water. Blow across the top of the bottle and observe the sound (pitch) coming from the bottle.
(2) Fill the next bottle with a little less water than the first bottle. Blow across the top of the bottle and observe the sound (pitch) coming from the bottle.
(3) Fill the remaining bottles with less water than the previous bottles. Blow across the top of the bottle and observe the sound (pitch) coming from the bottle.
(4) Now tap on the first bottle with a pencil. Observe the sound (pitch) coming from the bottle.
(5) Tap on the remaining bottles and observe the sound (pitch) coming from each of the bottles.
Conclusion
What did you notice about the pitch coming from the bottles as you blew on each one of them in descending order? Was there a difference in the pitch when you blew on the bottles than when you tapped on the bottle? Explain your answers.
Explanation
Different sounds are produced by changing the length of the object, or air volume through which the air vibrate. Shorter air columns produce higher pitches that longer air columns. When the glasses are tapped, they react in the same manner.
Lesson IV: Sympathetic Vibration
Materials Needed
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Four pieces of string 1 meter long
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Two items to support the string (chairs or tables will work perfectly)
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Three identical objects to be suspended from a piece of string
Procedures
(1) Attach one piece of string as tightly as possible between two chairs.
(2) Take the three remaining pieces of string and tie them at equal lengths apart on the string between the two chairs.
(3) Tie the weights at different heights to each of the three strings. Make sure that the knot can be easily undone.
(4) Once the weights are hanging in a still position. Swing the first weight from side to side like a pendulum.
(5) Observe and record what happens to the other weights along the string.
(6) Take turns swinging the other weights at separate interval and record what happens.
Conclusion
What happened to the other two weights when you swung the first weight? When you swung the other two weights? Why did this happen?
Explanation
When one of the pendulums along the line is set into motion, the other ones felt the tiny vibrations (resonance) traveling down the string. The second pendulum will begin to vibrate or swing (sympathetic vibration) because it is on the same natural frequency as the first pendulum. The same action causes the third pendulum to move.
Lesson V: Resonance
Materials Needed
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A variety of pots and pans
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String
Procedures
(1) Tie a piece of string around the handles of each of the pots and pans. Make sure they are secure.
(2) Tie each of the pots and pans to a strong support system. Make sure they are secure and will not fall during the experiment.
(3) Once all of the pots and pans are hanging safely and you are sure there is no chance of them falling continue with step four.
(4) Label each pot and pan A, B, C, etc..., until all the items are labeled.
(5) Sing a steady loud note into each of the pots and pans for a few seconds. Record your observations for each letter on a chart.
Conclusion
Did some of the pots or pans resonate better than others? If so, which ones? Do you think that the materials in which the pots and pans were made of make a difference in their resonating qualities? If so which ones?
Explanation
The students should hear a sound reflecting from the pans. Because some materials resonate better than others, the students may not hear anything when they sing a single note into a pan.
