Music to Your Ears

Music is usually considered to be one of the arts, but scientists are interested in sound and music too.

Take a few minutes to sit quietly and just listen. What do you hear? I hear the hum of the computer and the keys clacking as I type this. Do you hear your computer? Beside me I hear a cat purring, behind me the mice are rustling in their cage as they eat their morning snacks. Every once in awhile the parent birds in the shrub outside the window bring food back to their babies and the babies make a terrific racket. Further away I can hear doves cooing and once in awhile, a car passing. These sounds were all around me, but until I sat still and listened, I didn't really hear them. Why do you think that is true? What is sound anyway?

Let's investigate sound by creating some musical instruments. First gather a few materials. A clean, empty tin can with ridges makes a great start. Ask an adult to help you find one, perhaps from the recycling bin. Make sure it doesn't have sharp edges. Now find pencils or chopsticks, rubber bands, balloons, small plastic combs, and some clean, empty bottles with narrow necks.

Think about how you can make sounds using these items. The best musical instruments are the ones you design yourself, but here are a few ideas to get you started. Tap the can with the pencil. How does it sound? Now try rubbing the pencil across the ridges of the can. Try rubbing fast and then slow. You have made a simple guiro, a ridged instrument used in Central America. Do you have anything else with ridges to try?

You can also put a large balloon over the open edge of the can and fasten it down with a rubber band. This creates a cool drum. Or simply blow up a balloon and then hold the opening flat as you let the air out. Can you make a squealing noise? Blow up the balloon, tie it and drum on it.

Can you string the rubber bands across anything to make a guitar? Tie some rubber bands tightly and make others loose. Do they sound different?

What can you do with the bottle? How about blowing over the opening? Hold the opening of the bottle at your bottle lip, and then blow air across the top. This how the musical instrument called the flute produces sound.

Gently touch your various musical instruments while you are playing them. Do you feel anything? You should feel a wavering or vibration. If you are blowing a recorder, can you feel the vibrations on your lips? If you tap on a desk, can you feel the vibrations it makes?

Sound travels as waves, which you feel as vibrations as it passes through the instrument. Here on earth the waves can pass through air because it is made up of gases, and so you can hear someone calling you for dinner. What about in space, where there aren't any gases or substances for the sound waves to pass through? Scientists have predicted, and astronauts have verified, that sound does not pass through empty space.

Oh, I hear the phone ringing, time to go. Now I'm wondering how a telephone works!

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