A Simple Telephone

© 2007 Publications International, Ltd.

A Simple Telephone

In the past, when kids wanted to share a secret or play communication games, they'd use a simple telephone. It may not have been as cool as a cellphone or a walkie-talkie, but it was effective. Try this science project on producing sound to learn how a simple telephone works.

What You'll Need:

  • Pen
  • Nail or other pointed object
  • Two hard-plastic containers (such as cottage cheese containers)
  • String

Step 1: Use a pen to punch a small hole in the middle of the bottom of each of two hard-plastic containers, such as cottage cheese containers. Thread one end of a 12-foot piece of string through the hole in each container so that the end is inside the container. Tie knots in each end so the string will not pull out through the hole.

Step 2: Hold one cup, and give the other to a friend. Walk far enough apart so the string between the cups is pulled tight. The string should not be touching anything except the plastic containers.

Step 3: Ask your friend to hold the cup over one ear while you whisper into the other cup.

Your voice will make the string vibrate. The vibration will travel along the string to the other cup, and your friend will clearly hear what you whispered. Now listen while your friend whispers.

Build other phones that use different lengths of string and different kinds of containers, and compare how well they work.

Continue on to the next page to learn how volume and mass can produce bottle music.

For more science projects for kids, check out: