Homemade String Telephone

Project Overview: Build a classic string telephone and turn it into a real science experiment, testing how string material, cup material, and string length each affect how well sound travels.

Materials: 

•  Cup options (at least 2)

  • Paper cups

  • Plastic cups

  • Styrofoam cups

  • Empty cans

• String options (at least 2)

  • Yarn

  • Nylon

  • Dental floss

  • Twine

Instructions: 

1. Start with two paper cups and a 6m / 20ft length of cotton string. Use a toothpick or pencil tip to carefully poke a small hole in the bottom center of each cup. Thread one end of the string through the hole in each cup and tie a knot on the inside so the string can't pull through. This is your baseline telephone.

2. You and a partner each hold one cup. Walk apart until the string is pulled taut — do not let it sag or touch anything. One person speaks softly into their cup while the other holds their cup to their ear. Can you hear each other clearly? Rate the sound clarity on a scale of 1–3 and write it down.

3. Keep the same paper cups and 6m / 20ft length, but swap to a different string material. Test each one the same way and rate the sound clarity each time.

4. Using your best-performing string from Step 4, rebuild the telephone with different cup materials. Test and rate each one. Which cup transmits sound most clearly?

5. Using your best-performing string and cup combination from Steps 4 and 5, cut new pieces of string at 3m / 10ft and 12m / 40ft. Test each length and rate the sound clarity. Does the sound get weaker as the string gets longer?

6. Using everything you learned, assemble the best possible telephone — the combination of cup, string material, and string length that gave the clearest sound. Test it one final time and compare it to your original baseline.