Sound Waves

Ocean waves and sound waves have a lot in common, although sound waves are a lot harder to see. (Check out the "Seeing Sound" activity in Dr. D's Lab if you want to see sound waves.) On the right is a picture of an ocean wave. Click on it to view a picture of a sound wave captured on a computer. Look at the sound wave. Can you identify crests and troughs? How would you measure the amplitude and wavelength? Is anything missing from the graph that you would need? How would you measure the frequency?

If the amplitude of the waves in the ocean increases, what do swimmers in the ocean feel? What if the amplitude gets really big?

Changing the amplitude of a sound wave changes the loudness or intensity of the sound. Click on the sound waves below to hear what changing the amplitude sounds like. All three sound waves are the same guitar recording with only the amplitude changed.

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Sound: High & Low

Have you ever played a piano? Keys to the right side of a piano keyboard play notes that are higher than keys to the left (that play lower notes). The term pitch is used to talk about the "highness" or "lowness" of a sound. We say that the notes to the right of a piano keyboard have a higher pitch than the ones on the left.

The pitch of a sound is directly related to the frequency of the sound wave. Higher frequency means higher pitch. Lower frequency sound waves create sounds with lower pitch.

Changing the frequency of a sound wave changes the pitch of the sound. Click on each of the sound waves below to hear what changing the frequency sounds like. The sounds are different notes on a piano.