What type of wave is sound classified as?

Sound is classified as a mechanical wave because it requires a medium (such as air, liquid, or solid) to propagate; it cannot travel through a vacuum. Furthermore, sound is specifically a longitudinal wave, meaning that the oscillations of the particles in the medium occur in the same direction as the wave travels. In a longitudinal wave, particles compress and rarefy, creating regions of higher and lower pressure, which is characteristic of sound waves.

This distinction is crucial in acoustics and medical sonography, where understanding how sound behaves in different media influences imaging techniques. The classification as longitudinal also explains how sound waves can travel efficiently through fluids and solids, which is fundamental in ultrasound applications.