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Science

String telephone: How do materials affect how sound travels?

Scientists investigate.

Sound is made up of vibrations, or sound waves, that we can hear. These sound waves are formed by objects vibrating (shaking back and forth). Sound waves travel through air, water, and solid objects as vibrations. When they reach our ears, these waves make the delicate skids of the eardrums vibrate. Our brains recognize these vibrations as sounds made by different things. (Source: DK findout!: Sound)

Experience these vibrations by making a string telephone:

• You’ll need:

  • 2 disposable cups (paper, plastic, whatever you have)

  • sharp pencil, toothpick, paperclip, nail or scissors

  • string, yarn, dental floss, fishing line, or similar

  • (optional: 2 toothpicks or paperclips)

• Make a string telephone:

  • Punch a small hole in the center of the bottom of each cup (for plastic cups, you might need a nail or other sharp tool). Be careful with this step!

  • Thread one end of the string or yarn through each small hole.

  • Tie several knots in the end of the string to keep it from slipping out the hole. (Or, put a paperclip or toothpick in the bottom of each cup and tie the loose end of the string around it. The object will keep the string from slipping through the bottom of the cup.)

  • Try out your telephone. Have someone hold one end. Pull so that the string is straight. Can you hear each other talking?

• Investigate: Decide to change something (length of string, materials, how the string is attached to the cup). Talk about: What do you think will happen?

• Try it out. Talk about: What happened? Did you observe what you predicted? What new questions do you have?

• See video instructions from OMSI: The Science Behind String Telephones