Webs Wires and Waves: The Science & Technology of Communication

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Activity 1 Overview
Children will learn how sound is made--and how it travels--by creating and observing a vibrating "coat hanger clanger."

Estimated Time and Age Level
Advance Preparation: 10 minutes
Activity: 30 minutes
(Ages 7-11)

(Per child)
1 metal coat hanger
1 60-cm (2-foot) piece of cotton string

Divide the group into pairs. Children will need chairs with backs against which to hit their hanger devices. They could also use the edge of a table.

Cut one 60-cm (2-foot) piece of cotton string for each youngster. If you don't have enough metal hangers to go around, each team can share one hanger. However, since children will be holding one end of the string just inside their ears, they should change the string as they pass the device around.

Set out the materials in a central location.

Set the stage for the activity by asking the children what they think causes sound. They may suggest that sound is caused by talking, musical instruments, or electronic devices such as television sets. Write down their responses. After they do this activity, they can revise their ideas based on what they learn.

Have the youngsters make their "hanger clangers" by tying one end of a piece of string around the hook part of a hanger. Then ask them to hold the other end of the string just inside one of their ears and let the hanger swing freely against the back of a chair. The children will hear a ringing tone that will last for several seconds.

Now ask them again what they think causes sound. Give them time to confer with each other and to design new experiments to determine the cause and nature of the sound they hear, recording their observations after each experiment. For example, they might try:

Examining the hanger after it hits against the desk or chair. What is it doing? (Vibrating.)

Trying to alter the sound by changing the experiment through longer or shorter swings of the hanger or changing the hanger's shape.

Grabbing the hanger just after it hits the chair. What happens? (The hanger stops vibrating and the sound stops. By grabbing hold of the hanger, youngsters will be able to feel the vibrations as well as hear them.)

Even if children don't use the word "vibrating," they should be able to conclude that sound has something to do with objects that move rapidly back and forth. Have them try out other vibrating sound makers, such as plucking a stretched rubber band. Ask them to propose and record some other ideas about what causes sound. They'll have a chance to build on these experiences and revise their hypotheses after the following two activities.

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