My kids love science experiments. I can’t even begin to count how many ways we’ve played with vinegar and baking soda…. This week we made paper cup phones, something I remember doing as a child.
Materials needed for string and cup phones:
- 2 paper cups
- Length of string (we used yarn)
- 2 Paper clips (optional)
To make your own paper cup phones, use the tip of a pencil to poke a small hole at the bottom of each of your two cups.
Next, thread the string through the hole of one cup. We just tied a knot in the yarn on the inside of the cup to keep it in place. If the string keeps slipping through the hole you can tie it to a paper clip to help keep it in place.
Pull the string through the bottom of your second cup, securing it with an knot on the inside, too. (See photo above.)
To use your phones the string must be kept taut. When one person whispers in their cup, the other should be able to hear their voice through their own cup.
My daughter was thrilled to hear my voice being whispered in her ear from over 20 feet away!
Why does it work?
Sound waves can travel through air, solids, and liquids.
When you speak into the cup, the vibrations are transmitted into the string. They continue to travel through the string, as long as it is held taut, to the receiving cup. There the vibrations are transmitted to the air in the cup, around the listener’s ear, allowing the whisper to be heard.
Because the cup and string are solid, and solids actually carry sound waves better than air, the whisper can be heard much clearer than if you were to just whisper into the air from that distance.
Looking for more science fun to share with the kids? Check out our other science experiments!