Communication by Electricity

Seeing Speakers

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Prototype loudspeakers invented at the GE Research Laboratory, 1925

Description

This activity is a continuation of Activity #3: Vibrating Hangers, and will continue to expose students to the nature of sound waves.

Materials

White rice, 1 cup or less

Plastic wrap

A large speaker

Extended activity: a bowl, a metal tray/ sheet pan, metal spoon

Outline

1.      Tip the speaker onto its side so that the “drum” faces upward.

2.      Stretch a piece of plastic wrap tightly over said drum and place the rice grains on top.

3.      As you turn on the speaker, what happens to the rice grains? What happens as you change the volume and pitch?

Extended Activity

Adapted from https://coolscienceexperimentshq.com/how-to-see-sound/

If you cannot access a suitable speaker, instead stretch the plastic wrap over a bowl. Then, holding a metal sheet next to the bowl, strike the sheet with a metal spoon. What happens to the rice grains? How does their movement change as you change your striker or the object you strike? As you move further or closer away? Hit faster or slower?

Montgomery Ward Airline radio with built-in speaker, 1934