Objectives:
- Students will recognize that changes in an object can change the pitch it makes.
- Students will identify Cherokee water drums as an example of this phenomenon.
Materials:
- identical water glasses; at least three
- Mavalus tape
- Measuring Cup
- water
- Craft Sticks
Procedures:
- Explain that the Cherokee put water in drums. Ask for guesses about why they might have done this. Accept all answers as possibilities and leave the question open.
- Prepare the glasses by putting a small piece of Mavalus tape on each.
- Line up glasses. Have students measure out varying amounts of water and pour the water into the glasses. Use the Mavalus tape to record the amount of water used in each glass. All the amounts should be different, but avoid having any pattern to the quantities.
- Tap glasses with the craft stick and listen for differences. Ask students to describe the difference in the sounds.
- Students may say that the glasses sound higher or lower. Introduce the word “pitch.” Sing several notes and ask students to raise their hands if they hear a high sound and lower their hands if they hear a low note. Make certain that this concept is clear before moving on to the next step.
- Strike the glasses again and ask the students to line the glasses up so that the lowest notes are on the left and the highest notes on the right. Help students notice that the glasses with the largest amounts of water have the lowest pitch, and the glasses with the smallest amounts have the highest pitch. Write this out as a hypothesis.
- If students have other ideas, allow them to test their ideas.
- Once students are satisfied that a larger amount of water makes a lower pitch, write out a statement of the fact you have discovered.
- If you have discussed mass and volume, you can point out that putting water into the glass increases the mass and slows the vibrations.
- Return to the question of the Cherokee water drums. Why might the Cherokee have used water in their drums? To create drums of varying pitch.
- Allow students to try creating sound patterns with the glasses before cleaning up.
