The Sound Proofing Challenge

Ever enjoyed the sweet sounds of a pneumatic drill outside your bedroom window at 8am and wondered whether anything could be done about it (other than complaining to the council)?

It is possible to stop sounds from travelling from their source into your ears, but some materials are much more effective at doing this than others.

You will need:

* a kitchen timer
* a biscuit tin
* some foil
* some paper bags
* some damp newspaper
* a tea towel


What to do:

1. Set the kitchen timer and wait for it to go off. Loud isn’t it?

2. Now wrap it in foil and place it in a biscuit tin.

3. Put the lid on and wait for it to ring.

4. How does it sound now?

5. Repeat with the timer wrapped in the other materials in turn. Which one seems to be the most effect? Or what about a combination? Is it possible to block the sound out completely?


What's going on?

As you know by now, the sound produced by the kitchen timer RRRRINGING is a vibration which passes via air molecules to the ear. When the timer is wrapped in, say, a tea towel and then placed in the biscuit tin the RRRRRRRING vibrations have to pass through both the tea towel and the tin on the way to our ear in order for us to hear the noise.

However, vibrations can be absorbed and/or reflected by these other materials, which is why the resulting sound of the RRRRRRING is so much quieter. Soft materials such as felt are the most effective at doing this, while others, such as foil, will make very little difference at all. This is the reason why homeowners are often keen to have carpets – they reduce the sound of your footsteps for people below, and can even go some way to muffling the sound of your little brother’s drum practice. On the other hand, empty houses sound loud and echoey because there’s no furniture or floorcoverings to absorb the sound – so sounds reflect off the floors, walls and ceilings instead.