Here’s what you need to build your own:
What you need
1 piece of heavy string or thin yarn that is about 3 feet long
2 plastic yogurt cups (tin cans work too, just be careful of sharp edges)
Something to poke a hole in the bottom of each cup (and a big person to help you)
Two people to use the phones
What you do
1) Poke a hole in the bottom of each cup
2) Thread the string through the bottom of the first cup and secure it with a larger knot on the inside of the cup
3) Thread the other end of the string from the outside to the inside of the other cup and secure it on the inside with a large knot as well.
4) Each person gets one cup.
5) Pull the string tight between the two cups. This is very important. The string needs to be tight for the sound waves to travel along it.
6) Take turns talking in a low voice directly into one cup while the other person holds the other up to their ear to listen.
It may be hard to hear each other well through your new telephone because sound waves don’t travel as well over fuzzy string as they do in the air, but part of the fun is seeing how many silly things you each think the other one said! (Animal sounds are especially silly too!)