A String Phone

string phone

Sound waves are mechanical waves which can be propagated through a medium. However, our landline telephones used to convert sound waves into electric currents and sent it through wires. On the receiver’s end, the electric current will be converted back to sound waves. Let us see how our mechanical string phone operates.

Try it yourself

You need:

  1. 2 Plastic cups or paper cups
  2. A needle or a nail to pierce the cups
  3. A string that has almost 20 meters length (Fishing lines work good)
  4. A friend

What next?

Step 1: Pierce a small hole in each of the cup (just in the size to pass the string in)

Step 2: Insert one end of the string through one of the cup’s hole. Tie a knot on the string to stop it pulling through the cup.

Step 3: Repeat step 2 with the second cup and the other end of the string.

Step 4: Ask your friend to take one of the cup and stay away.

Step 5: Now take the cup in your hand and talk to it. Ask your friend to keep the other cup to his ears and listen to what you are talking.

Note what your experience is………You will feel great….

Step 6: Now without the help of your homemade phone talk and ask your friend to listen.

Compare the experiences.


Logic of string phone: When you speak into the cup, the sound waves create vibrations and this will travel through the string to reach the other end. Sound needs a medium to travel. Sound travels through air but it will travel better through solid.

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