Hanging Out with Sound

What you need:

A metal clothes hanger

String

Scissors

A spoon

A friend

What to do:

1. Cut out two lengths of string (about 15 inches each).

2. Lay the hanger flat on a table. Tie one end of each string to one corner of the hanger. Lay the strings out straight too, to ensure that both of them stay equal.

3. Now, loop the free end of each string around your index fingers. The hanger will hang upside down in this case.

4. Ask your friend to hit the hanger with the spoon. What do you hear?

5. Now, undo the loops and put the string, along with your index fingers, into your ears. Ask your friend to hit the hanger with the spoon again.

What happens:

The sound of the hanger hitting the spoon sounds quite loud and different when the string is inside your ear!

Why?

An object is said to ‘produce sound’ when it vibrates. These vibrations travel through the medium they are produced in (air, water or solid) and reach our ear. They make our eardrums vibrate thereby allowing us to ‘hear’.

The vibrations of sound travel better in a denser medium where molecules are packed closely together. They are able to move easily from one molecule to another. That is why you put your ear against a person’s chest to hear their heartbeat. You can’t hear the same heartbeat through the air.

Similarly, when the string isn’t in your ears, the sound of the spoon hitting the hanger travels through air and reaches your ears. But when the string is in your ears, the same sound travels through the hanger and the string and gets to your ear. The fact that your ears are connected to a dense, solid medium makes the sound different and loud!

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