Sound Waves Review

I CAN…

▹Identify the
characteristics of sound
waves.

▹Explain how sound
travels.

▹Describe the Doppler
effect.

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When an object vibrates, it exerts a force on the
surrounding air. For example, as the end of the
tuning fork moves outward into the air, it pushes
the molecules in the air together.

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As a result, a region where the molecules
are closer together, or more dense, is
created. This region of higher density is
called a compression. When the end of the
tuning fork moves back, it creates a region
of lower density called a rarefaction.

Making Sound Waves

Like other waves, a sound wave can be described by its wavelength and frequency. The wavelength of a sound wave is shown below. The frequency of a sound wave is the number of compressions or rarefactions that pass by a given point in one second. An object that vibrates faster forms a sound wave with a higher frequency.

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What determines the loudness of different sounds?

The amount of energy a wave carries depends on its amplitude. For a compressional wave such as a sound wave, the amplitude is related to how spread out the molecules or particles are in the compressions and rarefactions (seen as expansions below).

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