Waves can be classified by the way they displace matter

Longitudinal Waves and Transverse Waves  Mechanical waves are categorized by their type of motion and fall into any of two categories: transverse or longitudinal. Note that both transverse and longitudinal waves can be periodic and Like transverse waves, longitudinal waves do not displace mass. The difference is that each particle which makes up the medium through which a longitudinal wave propagates oscillates along the axis of propagation. ... Matter in the medium is periodically displaced by a sound wave, and thus oscillates.

Explanation:

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