First Grade · Science · week 5

String telephone: sound travels

Build a string telephone and observe that sound travels through the string to a listener's ear.

Sound does not just happen in one spot -- it travels. When you talk, vibrations move through the air to reach someone's ear. Sound can also travel through solid things, like a string, and it can travel very well that way.

A string telephone uses two cups and a tight string between them. When you talk into one cup, your voice vibrates the bottom of the cup, which vibrates the string, which vibrates the other cup, which the listener hears.

📋 For the teacher
Teach it (10–15 min):
  • Help poke the cup holes and tie sturdy knots so the string cannot slip out during use.
  • Insist on a taut string every test -- it is the single most important part of this experiment.
  • Let your child feel the string vibrating with their fingers while a third person talks, connecting back to the throat vibration from week 1.
  • Try talking without the string telephone at the same distance, so your child compares how much easier it is to hear with the string.
Talk about it:
  • What happened when the string went loose instead of tight?
  • What did the string feel like while someone was talking?
  • How is this like the drum or the rubber band from earlier weeks?

Mastery looks like: They explain that a tight string carries vibrations from one cup to the other, and that a loose string does not work as well.

Common stumbles: Letting the string touch something else, like a hand or a chair, which stops the vibration partway; not pulling the string tight enough to test fairly.

Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
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