Sound Waves

What do they look like?

How can you describe a sound wave?

You can see a picture of a sound wave on the screen of a device called an oscilloscope.

Look at the diagram above. The compressions, in which particles are crowded together, appear as upward curves in the line. The rarefactions, in which particles are spread apart, appear as downward curves in the line.
Three characteristics are used to describe a sound wave. These are wavelength, frequency, and amplitude.

Wavelength; this is the distance from the crest of one wave to the crest of the next.

Frequency; this is the number of waves that pass a point in each second.

Amplitude; this is the measure of the amount of energy in a sound wave.

Pitch

This is how high or low a sound seems. A bird makes a high pitch. A lion makes a low pitch.

Sounds also are different in how loud and how soft they are.
The more energy the sound wave has the louder the sound seems. The intensity of a sound is the amount of energy it has. You hear intensity as loudness.
Remember the amplitude, or height of a sound wave is a measure of the amount of energy in the wave. so the greater the intensity of a sound, the greater the amplitude.

Pitch and loudness are two ways that sounds are different. Another way is in quality.
Some sounds are pleasant and some are a noise.
Compare the two waves on the right.
A pleasant sound has a regular wave pattern. The pattern is repeated over and over. But the waves of noise are irregular. They do not have a repeated pattern.

Sound