Lesson Plan: Sound Vibrations

1. As a pre-assessment tool, and to activate prior knowledge, ask students:

• How are sounds made?
• How does sound get from the source (say, the teacher's mouth) to your ears?

Make sounds with several different instruments. For example, ring a bell or strike a triangle, xylophone, or drum. Ask students if they can see these instruments vibrating. Ask them how the sounds get from the instruments to their ears. Record their ideas on chart paper.

2. Introduce the word vibration and define it: a rapid back-and-forth movement. Demonstrate vibrations by blowing air through your lips and making "car sounds" or a "horse snort". Then show the Sound and Solids: Visualizing Vibrations video. After, ask students if they could see the vibrations in the water.

3. Show the Understanding Vibration and Pitch video. Then ask students to think of other things that vibrate (washing machines, toys, pagers, car engines, and so on). Have them touch their throat with the tips of their fingers and hum (or sing a song together). Ask them if they can guess how the humming sound is made. They should be able to feel their larynx vibrating. Tell them that the vibrations are what make the sounds. Next, ask students what other sounds they can make. Have them choose one.

• Does the sound have a high or low pitch?
• What is the volume of the sound -- is it loud or soft?

4. Show the Pitch: Straw Kazoo video. Then have students play their own straw kazoos (either made by you or by your students, using the instructions in the Pitch: Straw Kazoo (PDF) handout.) Ask students if they can feel the vibrations on their lips as they play the kazoo. Then ask them to think of words that describe the vibrations. Distribute several index cards to each student, and tell students to write one descriptive word per index card (or record them yourself if they are pre-literate). Then, as a class, arrange the words to make a vibration poem.

5. Demonstrate sound vibrations by placing a ruler on the edge of a desk, such that about eight inches of it hangs over the side. Place one hand on the four inches that remain on the desk, to hold the ruler securely. With your other hand, whack the end of the ruler that is hanging off of the desk. The ruler will vibrate up and down and produce a low sound.

Tell students to try this themselves. But before they get started, ask if they can think of a way to make the sound higher (demonstrate with your voice the difference between low pitch and high pitch). Take suggestions from students, but don't give away the answer; let them experiment with the rulers. After five minutes or so, collect the rulers and ask what they discovered (shortening the amount of ruler that hangs off of the desk causes the ruler to vibrate faster when it is struck, thus raising the pitch). Ask students what they think will happen if they use a yardstick instead of a ruler. Try it (optional).

6. Using the drum made earlier from a can and balloon, beat the drumhead (stretched balloon) with a drumstick (a chopstick or the eraser end of a pencil). Ask students if they see any vibrations (they won't). Then ask if they can hear them (they will). Explain that although it is hard to see, the drumhead is vibrating. Second graders will likely be able to make the connection between the sounds produced by their vibrating throats and rulers, and the sound produced by the vibrating drum. But before telling students that vibrations from the drumhead travel through the air to their ears, you might ask them for their ideas first.

7. Next, demonstrate three ways in which your students will be able to visualize vibrations:

• Put a few grains of rice on the drum and gently tap the drum with a drumstick. The vibrating drumhead will cause the rice to bounce. Next, speak loudly right next to the drum. Vibrations will travel from your mouth, through the air, and through the drumhead, once again causing the rice grains to bounce.
• Place a drum on the speaker of a portable radio/CD player. You may need to tip the player so that the speaker faces up. Put some rice on the drumhead and ask students to predict what will happen when you turn the radio on. When you turn on the radio, the vibrations from the speaker will travel through the air (and the sides of the drum), to the surface of the drum, causing the drumhead to vibrate and the rice to bounce.
• Turn off the radio and put a small mirror (reflective side up) on the surface of the drum. Turn off the classroom lights. Direct a laser pointer at the mirror, such that it reflects the laser beam onto the ceiling. Ask students what they think will happen to the light spot on the ceiling when you turn on the radio. Then turn on the radio. As the music plays, the light spot will bounce around on the ceiling. Explain that the vibrations from the radio caused the mirror to vibrate, which in turned caused the reflection of the laser beam to bounce around. Have students place their hands on the speaker as the music plays. They will be able to feel the vibrations.

8. If your students have the skills to make their own drums, then let them do so. If not, hand out pre-made drums for them to play. Also, hand out drumsticks and grains of rice for them to bounce on the drumhead. Students may notice that different drums produce different sounds. Some drums may be higher or lower in pitch. Remind them of the ruler experiment, and explain that, if all other variables are equal, the size of the drum is related to the pitch of the sound it makes, just as the length of the ruler was related to pitch. If students are making their own drums, you can challenge some to make a drum with a very low sound, or a very high sound.

9. Show the Hana's Japanese Drums video. Challenge students to use the drums to create their own music, just like Hana does. Ask them to arrange the cans in order from highest pitch to lowest.

10. Optional: Make a guitar from a tissue box and rubber bands. You can either make one for the class or ask teams of students to make their own. Follow the Pitch: Making Guitars activity instructions. Students' concept of vibrations will be reinforced when they see the guitar strings (rubber bands) vibrating as the guitar is played. Also have students watch the Kid Musician: Mexico's Guitar Town video to see real musical instruments in action.

11. Watch the Sound and Solids: Listening Stick video. Can your students think of other solid items through which vibrations can travel? List their ideas on the board or on chart paper. Some possible objects to test are sneakers, paper towel tubes, juice boxes, a student's arm, and foam pipe insulation. Create a chart of the items students will test, or use the Testing Solids Chart (PDF) provided. Ask students to predict whether the vibrations will travel very well (they'll hear the sound loudly at the other end), moderately well (they'll hear it, but not loudly), or not at all (they won't hear anything). Then ask them to test their predictions. Have them record the results on their own copy of the chart. Ask:

• What conclusions can you draw about the materials you used?
• Which materials would you like to line your room with in order to keep out sounds?
• Which materials would make good musical instruments?

12. As a follow-up, ask students how well they think vibrations will travel through string. Then read the Sound and Solids: Stereo Hangers (PDF) handout and test it out!