Transverse acoustic wave

Professional Definition

A transverse acoustic wave (often referred to as a shear wave) is a wave in which the direction of particle vibration in the medium is perpendicular to the direction in which the wave is propagating.

The occurrence of this type of wave is only possible in media that possess shear elasticity, meaning the ability to carry shear stresses. For this reason, transverse waves can propagate in solids, but do not occur in gases (air) or liquids (water), as these media cannot "slide" adjacent layers sideways under the influence of shear forces.

Acoustics in Simple Terms

Imagine a "Mexican wave" in a stadium. Fans stand up and sit down (perform a vertical motion), but the wave itself travels along the stands (horizontal motion). The direction of people's movement is perpendicular to the direction of the wave's movement.

Another great example is the guitar string or a rope tied to a wall:

• When you yank it hard, you see a "bump" racing toward the wall.

• The rope at a given point does not move toward the wall – it only moves up and down.

This is the essence of a transverse wave: energy travels forward, but the "building blocks" of the wave (particles, string, people) vibrate across that path. That's why when you hit a metal beam with a hammer, the energy travels through it partially as such "oscillation" of the material sideways.

Summary

• Direction of vibration: Particles move perpendicularly (across) to the direction of sound propagation.

• Medium: Exists only in solids and on strings – never in the air itself.

• Application: Key in vibroacoustics (study of machine vibrations), geophysics, and in the analysis of string instruments.