Exploration Lab

Investigating Sound Waves

Sound is produced when a vibrating source causes a medium to vibrate. In this lab, you will investigate how the vibrating source affects characteristics of the sound produced.

Problem

What determines the frequency and amplitude of the sound produced by a vibrating object?

Materials

• meter stick

• two cardboard tubes

• scissors or scalpel

• two rubber bands

• wax paper

• balloon

• small mirror

• transparent tape

• flashlight

Skills

Observing, Inferring, Drawing Conclusions, Controlling Variables

Procedure

Part A: Investigating How Length Affects Pitch

1. Hold one end of a meter stick down firmly on a table so that 20 centimeters of the meter stick extends past the edge of the table. Pluck the end of the meter stick that extends past the table to produce a vibration and a sound as shown. Observe the vibration and sound of the meter stick.

2. Repeat Step 1, but this time allow 40 centimeters of the meter stick to extend past the edge of the table. Observe and record how the length of the vibrating part of the meter stick affects the pitch.

3. Repeat Step 1, but this time allow 60 centimeters of the meter stick to extend past the edge of the table. Record your observations.

4. Investigate the relationship between length and frequency for a vibrating column of air, as you did with the vibrating meter stick. Make a kazoo by cutting a hole in the middle of one of the cardboard tubes. Make the hole approximately 1 centimeter in diameter. Use a rubber band to fasten the piece of wax paper over one end of the tube. CAUTION Be careful when cutting with sharp instruments; always cut away from yourself and away from nearby people.

5. Make a second kazoo by cutting the second tube 10 centimeters shorter than the first tube. Using the short tube, repeat Step 4.

6. Hold the shorter kazoo in front of your mouth and hum into the open end, keeping your pitch steady. Repeat this action with the longer kazoo, making sure to hum exactly as you did before. Observe and record how the length of the kazoo affects the pitch of the sound.