Ear Guitar 
Two kids listening

  • nail (you'll also need a hammer if you use tin cans)
  • two empty yogurt cups (you can also use two tin cans)
  • scissors
  • string
  • bar of soap
  • paper clips
  • a friend

 
Use the nail to poke a hole in the center of the bottom of each yogurt cup. (If you use tin cans, have a grown-up make a hole with a hammer and the nail.)

 Cups

With your scissors, cut a piece of string that's about 15 feet long.

 Putting the string through


Wet the bar of soap. Rub one end of the string on the soap, then roll the string in your fingers so it's pointy. Poke the end of the string through the hole into the cup.

  Reach into the cup with your fingers and pull the string a few inches. Tie the end of the string to a paper clip.

 Pulling the string

Do steps 3 and 4 again with the other cup and the other end of the string.

Now you've got an Ear Guitar! Hold one cup up to your ear, and give the other cup to your friend. Tell your friend to walk away from you until the string is tight, then hold his cup up to his own ear. When one of you plucks the string, both of you can hear the sound!

Is the sound you hear when you pluck the string different from the sound when your friend plucks the string? Does the sound change when the string is tighter or looser?

Tell-a-Cup

You can also use your Ear Guitar as a telephone! Have your friend walk away until the string is tight. Hold your cup up to your ear, and have your friend talk into her cup. Can you hear what she's saying?

 Make sure the string is tight

What's going on?

How does the Ear Guitar work?

When you pluck the string on an Ear Guitar, the string starts vibrating. The vibration in the string starts the bottom of the cup vibrating, which starts the air inside the cup vibrating. The cup helps channel those vibrating air molecules into your ear-so you hear the sound loud and clear.

Your voice, like other sounds, is a vibration. (Put your hand on your throat as you talk and you'll feel the vibrations.) When you talk into one of the cups, the vibrations of your voice travel into the cup, then from the cup into the string, and then back into the other cup. The cup channels your voice into your friend's ear.

Your yogurt-cup telephone works if the string between the two cups can vibrate freely. Pinch the string between the two cups, and your friend won't hear your voice as well. You may also discover that the string between the cups must be pulled tight, or your telephone won't work. If the string is loose, the sound vibrations die out before they reach the other cup.


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This and dozens of other cool activities are included in the Exploratorium's Science Explorer books, available for purchase from our online store.

About the Books

Published by Owl Books,
Henry Holt & Company, New York,
1996 & 1997

ISBN 0-B050-4536 & ISBN 0-8050-4537-6,
$12.95 each






© 1998 Exploratorium