String Telephone

A string telephone demonstrates how sound vibrations can travel through a medium. When you speak into one cup, vibrations move through the string and are amplified in the second cup, allowing a friend to hear your voice.

1. Use a push pin to poke a small hole in the bottom of two paper cups (adult supervision recommended).
2. Cut a length of string (10 feet or longer) and thread it through both holes.
3. Tie a paper clip to each end of the string or tie a knot inside the cups to keep it from slipping out.
4. Have two people each hold a cup and walk apart until the string is pulled tight.
5. Speak clearly into one cup while the other person listens through the second cup.

String Telephones - TeachEngineering:

📄 Make a String Telephone - Virginia 4-H: https://ext.vt.edu/content/dam/ext_vt_edu/topics/4h-youth/makers/files/ww1-telephones.pdf

• Use fishing line, yarn, or embroidery thread instead of string.
• Try different cup materials (plastic, paper, metal) or cup sizes.
• Make a three-way call by attaching multiple strings to one cup.
• Test what happens when the string is slack or when you touch it during transmission.

• Adult supervision required when using push pins or scissors.
• Do not pull the string too tightly—it may snap back.

• What happens when the string is tight versus loose? Why?
• How does sound travel from one cup to the other? (Through vibrations in the string.)
• What happens if you hold the string while someone is talking? Why is it like muting the line?
• How does this experiment compare to how landline telephones or cell phones transmit sound?
• Which materials made the clearest string telephone? Why do you think that is?