How to Make a Tin Can Telephone With a Plastic Cup and Will It Work?

The string has to be kept tight to allow the transmission of vibrations between the cans.

Tin can telephones were a homemade staple for kids before the invention of multiple phone lines and cell phones. Kids could even stretch their strings from house to house and have conversations. The updated version, made with two plastic cups, works on the same principle of physics that the tin can version does but the flexibility of the plastic makes the sound wave transmission less crisp than the vibrations from the metal can. This makes the plastic cup less efficient but still viable for use in a string based "telephone."

Things You'll Need

• Two plastic cups
• String
• Scissors

Instructions

1. Poke two small holes in the bottom of each cup with the pointed end of the scissors.

2. Thread a piece of string through one of the holes from the bottom of one cup.

3. Thread this string back through the bottom of the cup through the other hole.

4. Tie the string in a knot tight against the bottom of the cup. Repeat this process for the other cup.

Tips & Warnings

• For the transmission of sound to work, you and a friend have to pull the string tight and one of you must talk into one cup while the one at the other end listens. The sound waves that are released from the speaker's mouth are transmitted via vibrations in the string to the other cup where they are returned to audible form by the flexing of the cup bottom.

• If the string is not tied tightly then there can be a loss of vibration and the sound transmission may be lost.

References

• CSIRO; Science by Email; "Try This: Tin Can Telephone"
• University of Wisconsin; "Build a String Telephone"; September 2007