The Tin Can Telephone

If you’ve never taken a call on a tin can telephone, you simply haven’t lived. This is a classic activity, some say Alexander Graham Bell enjoyed it as a boy.

You will need:

* two tin cans, thoroughly washed, and with a hole punctured in the bottom. (NB if you’re under 12 get an adult to both make the puncture hole, and to bend all sharp edges inside the can for you.) If in doubt, use plastic cups instead.

* a length of string

* a friend

* some spectacularly idle gossip to impart


What to do:

1. Thread the string through the holes in the cans or cups, and secure with knots at either end. NB You need to have the knots inside the cans!

2. Take one can – er, telephone receiver – and get your friend to take hold of the other.

3. Now move away from each other until the string is pulled taut.

4. Now sort yourselves out so that one person speaks into the can, while the other positions the phone over their ear.

4. Now let rip with that gossip.

5. NB watch out – if a third party tries to tie a string with another can on it to your phone line, they will be able to listen in. So change the subject quickly!


What’s going on:

As you’ve seen already, noise travels very effectively through a solid object, much better than it does through the air. So, when you speak into the can, the vibrations travel along the string, to the other can, where they can be heard distinctly by your friend.

Don’t try listening round corners though, because if your string comes into contact with anything, like a brick wall for example, all those vibrations will be lost and never reach the other can…