Oct. 22, 2003

Whirl a Bull-Roarer

For thousands of years, bull-roarers have been used by various cultures in ceremonies. The sound made by the bull-roarer as it whirls through the air represents the voices of spirits and thunder. Here's your chance to make your own modern bull-roarer.

You'll need:

• scissors
• a cardboard carton with flaps about 30 cm (12 inches) long
• a pencil
• tape
• 6 thick rubber bands

What to do:

1. Cut off two flaps from the open end of the carton.
2. On one flap, draw a long oval shape that is 30 cm (12 inches) long and 6 cm (2 1/2 inches) wide.
3. Make two more ovals by tracing the first one onto the cardboard. Cut them out.
4. Pile the three ovals one on top of the other. Tape the edges to hold the ovals together.
5. With the point of the scissors, make a hole through all three layers 2 cm (3/4 inch) at one end of the oval.
6. Join the rubber bands together to make a long rubber chain. (To join one band to another, overlap the ends to make a small hole. Put the end of the underlying band through the hole and pull tightly.)
7. Push a part of the last rubber band through the hole in the cardboard. Bring the rest of the chain over the end of the oval, thread it through the end of the rubber band and pull. The chain should now be firmly attached to the oval.
8. Whirl your bull-roarer in an open area away from people. To do this, hold the free end of the chain and rapidly whirl the bull-roarer around in a circle above your head.

How does it work?

As you whirl the bull-roarer through the air, the oval or blade is spinning around rapidly. You can see this when you let the blade hang down immediately after you've stopped whirling it. The spinning blade pushes against the surrounding air molecules causing the air to vibrate. These vibrations travel to your ears as sound. The whirling blades of a helicopter make a noise for the same reason. Their noise is much louder than a bull-roarer's because the blades are larger and there is more than one rotating.

Activity from Sound Science by Etta Kaner and illustrated by Louise Phillips, is used by permission of Kids Can Press Ltd. (www.kidscanpress.com). Text copyright © 1991 by Etta Kaner.

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