Experiments: Sound


Materials you need are:
a thin strong length of timber (like a metre ruler)
a length of string

Tie the string to the length of timber as shown in the diagram below. Hold it above your head and swing it around as fast as you can and as long as you can.

Bullroarer Diagram

The movement of the timber through the air creates a deep droning sound. Indigenous Australian men used the bullroarer to summon tribesmen to meetings.

Ringing in your Ears

Safety rules:
Parent supervision
Take care with scissors

Materials you need are:
a length of fine string (about 1 metre long)
2 teaspoons

Tie one spoon in the middle of the string. Hold the two ends to your ears. Ask a friend to tap the tied spoon with the other spoon. Compare the sound of this with the sound of tapping them without the string in your ears.

Sound waves travel faster through solids than through liquids and gases, so when the string in near your ears, the clinking of the spoons should sound louder than in air.

Make a String Telephone

Safety rules:
Parent supervision
Take care with scissors, nail and hammer

Materials you need are:
2 empty cans that fit over your ear
a length of string (about 4 metres long)
a nail
a hammer
a friend

Make a small hole in the centre of the base of each can with the hammer and nail. Put the end of the string through the hole in one can and tie a knot so the string doesn't fall out. Do the same with the other end of the string and the other can. Give one can to each person and pull the string tightly. To speak, talk into the can. To hear, hold the can to your ear.

Because sound travels better through solids than through the air, the voices travel relatively well along the string and are amplified by the can.

Make a Hydrophone

Safety rules:
Parent supervision for testing the hydrophone in a pool

Materials you need are:
a length of plastic tubing
a plastic funnel
a balloon (the round type) or a sheet of rubber and a strong elastic band

A hydrophone is an instrument for listening to underwater sounds. Stretch the balloon over the cone of the funnel. Tightly fit the funnel into one end of the rubber tubing. This is the part that goes underwater. Put the other end near your ear so you can hear. (Remember that you should not put anything into your ear in case you damage the eardrum.) Try it in a swimming pool with an underwater friend talking to you while you keep dry.

Musical Glasses

You will need a drinking glass with a fine rim (e.g. a crystal wine glass).

Dip your finger into some water and then gently rub your wet fingertip around and around the rim of the glass until it makes a high-pitched sound.

Musical Bottles

Fill several glass bottles to different heights and strike them with a spoon gently to make a tune.