Seeing Sound 1

Sound is a vibration that can only usually be picked up by our ears – or you might feel it booming through your whole body if it’s a loud enough, deep enough note.

You see a sound itself – but this activity will enable you to see the vibrations that cause the sound your ears are picking up.

* cling film
* a jam jar
* grains of rice, or unpopped popcorn…
* elastic band


What to do:

1. Place a piece of cling film over the top of the jam jar and pull it tight.

2. Put an elastic band over the neck of the jam jar to keep it extra taut.

3. Place a few grains of rice or corn on the cling film.

4. Take a deep breath and bellow loudly at the rice grains. Make sure your face is quite close to the jam jar. Think: Sergeant Major!

5. Watch what happens to the rice grains as you shout. "Come on! You ‘orrible shower!"

6. Try shouting with a deep voice and with a high voice, loudly and softly – what happens?


What's going on?

When you shout, your vocal cords vibrate. This causes air molecules to vibrate, moving backwards and forwards. This is a "sound wave". As the air molecules vibrate backwards and forwards, the movement is passed on to surrounding molecules, including those in the cling film. Consequently the molecules in the cling film also vibrate and this vibration is transferred to the grains of rice, which jump up and down.

What you’re seeing is the effect of the sound waves hitting the cling film. Groovy eh?

We hear different sounds from different vibrating objects because of variations in the sound wave frequency. A higher wave frequency simply means that the air pressure fluctuation switches back and forth more quickly. We hear this as a higher pitch. When there are fewer fluctuations in a period of time, the pitch is lower.

The wave's amplitude determines how loud the sound is. When shouting with a high voice, the rice grains should jump around faster; when shouting most loudly the rice grains should jump higher.

good vibrations

Most people detect sound with their ears, but you can also sense sound through your body, as well as see it with your eyes, as you’ve just done.

The world famous percussionist, Evelyn Glennie, is profoundly deaf - but she hasn’t let that stand in her pather to success for a single moment!

Read all about her experience of sound and music on the Evelyn Glennie website.