Ding Dong Dead

If sounds are caused by vibrations, what happens when you stop a vibration in its tracks?

You will need:

* a plastic bottle with a wide-ish top
* a bowl
* a pencil


What to do:

1. Balance the bowl upside down on top of the plastic bottle.

2. Hit the bowl with the pencil. Can you hear it ring? DING! Beautiful.

3. Now hold the edge of the bowl. Hit it again, just as hard as before. Do you notice how the sound goes ‘dead’?


What's going on?

As you’ve already discovered, sound is caused by vibrations, and it travels away from the source to your ears in a wave.

In this activity, when we DING the bowl, it makes a noise, because the molecules within the bowl to start to vibrate backwards and forwards. This in turn causes the air molecules near the bowl to vibrate backwards and forwards, and the vibration finally reaches our eardrums.

When you hold on to the bowl, your hand acts as a damper, absorbing most of the vibrations instead. Because you’ve prevented most of the vibrations from travelling through the air, your eardrums don’t vibrate much and consequently you don’t hear a loud sound any more.