Longitudinal waves

A longitudinal pulse is a disturbance with particle motion in the direction of travel.

Longitudinal pulses are observed on slinky-type springs and are most commonly encountered as propagating compressions in air, or another elastic medium.

A series of propagating compressions is a sound wave. Longitudinal seismic waves propagate through the Earth following earthquakes. On springs, rods etc. longitudinal waves have higher velocities than transverse waves.

Note: longitudinal waves cannot be polarized and longitudinal standing waves are difficult to draw. By convention we draw a transverse sine wave to represent the nodes (positions of high pressure) and the antinodes (positions of low pressure).

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