Wire Your Own String Phone!
Make a working string telephone using cups and string; test sound transmission, measure distance effects, and learn about vibrations and sound waves.
Step-by-step guide to wire your own string phone
Step 1
Gather all materials and move to an open space where two people can walk apart easily.
Step 2
Use the measuring tape to measure about 10 meters of string and cut it with scissors.
Step 3
With adult supervision make a small hole in the center of the bottom of the first cup using the tip of a pencil or scissors.
Step 4
With adult supervision make the same small hole in the bottom center of the second cup.
Step 5
Thread one end of the string through the hole in the first cup and tie a big knot inside so it can’t pull back through.
Step 6
Thread the other end of the string through the hole in the second cup and tie a big knot inside so it can’t pull back through.
Step 7
Walk apart and hold the cups so the string is straight and not rubbing on anything and keep the string tight.
Step 8
Have one person speak into their cup while the other puts the cup to their ear and listens to test the telephone.
Step 9
Put a finger lightly on the string halfway between the cups while someone talks to feel the vibrations traveling along the string.
Step 10
Measure 1 meter between you and the other person keep the string tight and test the sound again.
Step 11
Move to 3 meters apart keep the string tight and test the sound again.
Step 12
Move to 6 meters apart keep the string tight and test the sound again.
Step 13
Let the string go slack and have the speaker talk while the listener listens to compare how slack versus tight string changes the sound.
Step 14
Share a photo or short description of your working string phone and what you discovered about vibrations and distance on DIY.org
Final steps
You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!
Help!?
What can we use if we don’t have the exact materials like measuring tape, string, or paper cups?
If you don't have the 10 meters of string or a measuring tape, use 10 meters of yarn or twine measured with a meter stick or about 10 arm spans, swap paper cups for plastic cups or empty tin cans, and make the small hole with a needle or thumbtack under adult supervision.
Why can’t we hear each other well and how do we fix it?
If the sound is faint, make sure each hole is a small hole (made with the tip of a pencil or similar), tie a big knot inside each cup so the string can't pull back through, and walk apart keeping the string straight and tight without rubbing on anything.
How should we change the activity for different ages?
For younger kids have an adult make the holes and pre-cut a shorter string and start at 1 meter so they can focus on speaking and feeling the vibrations, while older kids can cut the full 10-meter string themselves and test the 1-, 3-, and 6-meter distances and try different string materials.
How can we extend or personalize the string phone activity once it works?
To extend the activity, decorate the cups, add a small bead on the string to visibly show vibrations, record sound quality at 1, 3, and 6 meters and photograph your setup to share what you discovered about vibrations and distance, and experiment with different string types.
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Facts about sound and vibrations
🎧 Sound travels as vibrations — your voice makes the cup vibrate, those vibrations travel along the string, and your friend’s cup turns them back into sound.
🔩 Tightening the string makes voices clearer because waves move with less energy loss when the line is taut.
🧵 Material matters — a smooth, low-stretch string (like nylon) usually carries vibrations better than a loose, fluffy yarn.
🥤 The cup acts like a diaphragm: it changes air pressure waves from your voice into mechanical vibrations the string can carry, then back into sound at the other end.
🧪 Tin-can telephones are classic hands-on science toys used for centuries to explore waves, tension, and how sound travels.
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