HEAR ME OUT

Make a tin can telephone

RN: 10082701 - PHYSICS > ACOUSTICS

SUITABLE GRADES

3 & 4

DIFFICULTY

2

TIME REQUIRED

<12 hrs

SUPERVISION

ADVISED

INTRODUCTION [METHOD]

When you speak, soundwaves are created by vibrations or back and forth movements in the air. In other words, one can say that the air gets compressed and decompressed by these sound waves in the air. When a friend speaks to you, the sound waves 0r 'compressions' created by his voice travels through the air, and when it reaches your ear it in turn let your eardrums vibrate or 'compress' enabling you to hear the sounds. If your friend speaks quietly or whispers, you will not be able to hear him and you will need a telephone – here is how to make one:

STUFF YOU NEED [MATERIALS]

2x TIN CANS
THICK TWINE
HAMMER
NAIL
A FRIEND

HOW TO PROCEED [PROCEDURE]

Obtain two tin cans with clean edges that were not opened with a tin opener. Small coffee tin cans would work well.
Use a hammer and a steel nail to make a small hole in the bottom of each of the tin cans. The holes need to be just wide enough for the twine to be pushed through.
Get a piece of twine of about 6-12 metres, thread the twine through each of the holes and tie a large knot on each end to prevent the twine from pulling out. Other solid materials can also be used eg. wire that you may play around with to get the best results.
Give one of the 'phones' (tin cans) to your friend, take the other one and walk away in opposite directions, until the twine is stretched out and makes a tight line.
Your phone is now ready to use! Ask you friend to speak into the can in a manner that you would normally not be able to hear, and you should be able to hear his voice quite clearly!

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GLOSSARY [TERMS]

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