Make a Cup-and-String Phone

1. 1

   Make a classic cup-and-string telephone and explore how it carries sound.

2. 2

   Connect two paper cups with a length of string. Have your child hold one cup to their ear while you pull the string straight and speak into the other cup.

3. 3

   After listening with the string tight, let it hang loose and try again.

4. 4

   Ask what changed and whether the difference might be related to the string. Invite your child to test the idea.

5. 5

   Move closer and farther apart so the string alternates between loose and tight, taking turns speaking and listening.

6. 6

   When your child identifies the clearest setup, invite another family member to try and let your child share the result.

What to notice

• Loosens and tightens the string and compares how the sound changes Reasoning and Problem-Solving
• Tells you what they observed, such as “It only makes a sound when I pull it straight.” Communicating and Speaking

Tips

• If the sound is faint, treat the result as information rather than a failure. Help your child say, “It wasn’t very clear this time. What might have changed?” This invites them to notice a problem and adjust the experiment.

Developmental benefits

• Cognitive: Making a cup-and-string telephone and comparing what happens when the string is tight or loose gives your child practice testing an idea and comparing results.
• Language: Describing how the sound changes with the string’s tension gives your child practice turning an observation into a clear explanation.