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How to Make a String Telephone

At some point in most children̵7;s lives, they play with a homemade telephone. They use string and two cans or cups strung between two locations to talk with each other. This simple toy isn̵7;t perfect but it does work. The propagation of sound along the string illustrates many principles of sound waves and their behavior. The sound waves move from one location to another by traveling along the string. Make your own string telephone using items you find in your garage or kitchen.

Things You'll Need

Nail
Hammer
2 disposable cups or tin cans
String
Tape

Instructions

- 1
  Use a nail to poke a hole in the center of each of the cups or tin cans. Paper or plastic drink cups will both work but a plastic cup will be more durable. The cups or tin cans, whichever ones you decide to use, will be the receiver of the telephone. You will talk and listen to the sounds that come from the inside of them.
- 2
  Cut a length of string long enough to reach from one location to another. Allow a few extra inches so that you can move the cup or can slightly.
- 3
  Thread the end of the string through each cup or tin can from the bottom and into the center of the cup or can. Pull the string out until you have enough room to tie a knot in the end of the string. The knot will keep the string from coming loose from the cup or can.
- 4
  Tie a knot at each end of string. You may need to tie a double knot to keep the string from pulling out of the hole in the bottom of the cup or can.
- 5
  Pull the strings tight against the inside bottom of the cup or can and place a piece of tape over the string to hold it firmly against the bottom.
- 6
  Pull the string tight and speak into the cup or can while the other person listens. You will hear the other person speaking at the other end of the string. If you do not hold the string tight, you won̵7;t hear anything.

Educational Toys