A sound is a very quick vibration. We can hear and feel many sounds.

You can hear lots of sounds such as voices, the sound of breaking glass, and musical instruments such as cymbals being clashed or a drum being struck. But how do you think they make the sounds we hear?

Feeling sound
You can actually feel sound being made by placing your finger gently onto the surface of a loudspeaker while it is working. You will feel the loudspeaker moving back and forth very quickly. This kind of movement is called a vibration.

If you tap an instrument such as a drum or tambourine and gently feel the skin, you can feel the vibrations. You can also pluck the string of a guitar or violin and feel the string moving up and down – it is also vibrating. If you place a finger gently on the lower part of your throat and sing a deep note, you can then feel your throat vibrating too. Where there is a sound, there is a vibration.

Seeing vibrations
Vibrations can be seen, as well as felt and heard, by using a tuning fork and a piece of cling film. The cling film needs to be tightly stretched over a jar and then covered in very fine grains of sand or rice. When the tuning fork is struck and placed so that it lightly touches the cling film, the vibrations will make the sand or rice on the film jump up and down.

Vibrations pass through air
You can see vibrations pass through the air by using a candle, a cardboard tube and some thin plastic. Stretch the plastic tightly over both ends of the tube and make a small hole in the centre of one piece of plastic. When the far side of the tube is tapped sharply, the air inside the tube is squashed slightly. As the air is forced out of the tube through the small hole, the energy in the squashed air is concentrated. As a result, a pattern of vibrating air comes out of the hole and makes the flame wobble in time with your tapping. You can make a candle do the same by clapping near to it.