Science Activity: Whisper Tubes

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Did you ever whisper a secret in someone's ear? If you did, you were aiming sound waves toward his or her eardrum. In this activity, you'll make some devices that will let you whisper to someone without speaking into his or her ear!

1. Get Ready

Four cardboard tubes from rolls of paper towels
Masking tape
Cookie sheet
Book
Table near a wall
Paper and pencil
Partner

2. Do and Wonder

First make two whisper tubes. To make each, put the ends of two cardboard tubes together and tape them very tightly. Use plenty of tape to do this so the tubes don't bend or sag in the middle.

Move the table against a wall. Put the cookie sheet on the table so it's vertical and pressed right against the wall. Use the book to hold the cookie sheet in this position.

Next you'll be aiming sound waves toward the cookie sheet. Lay both whisper tubes side by side on the table, so they're pointing toward the cookie sheet. Then move together the ends of the tubes nearest the cookie sheet, forming a V shape. The bottom of the V should be about 1 inch (2.5 centimeters) from the cookie sheet.

Have your partner put his or her ear up to the open end of one tube while you whisper into the open end of the other tube. Adjust the positions of the tubes until your partner can hear your whispers coming from the tube. Try softly whistling into one tube while your partner listens from the other.

Switch roles and repeat the experiment.

Make a labeled diagram that shows the source of the sound waves and the path they took from one whisper tube to the other.

3. Think and Write

Write a hypothesis that explains echoes. Here are some hints to help you: An echo needs a solid, flat surface for the sound waves to bounce off. If you're standing far away from a wall and yell toward the wall, you'll hear the sound made in your own voice box immediately.

Explanation

Sound waves carry energy from one place to another. When sound waves hit a surface, they bounce off it. The direction they come from determines the direction they will bounce. Using a whisper tube, you aimed sound waves at a reflecting surface- the cookie sheet. If you put the tube you whispered into in the right place, the sound waves traveled through your tube, bounced of the cookie sheet, and entered your partner's tube. That's how he or she was able to hear you!