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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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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.)
With your scissors, cut a piece of string that's about
15 feet long.
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.
Do steps 3 and 4 again with the other cup and the other
end of the string.
N
ow 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?
