A sound wave is a mechanical longitudinal wave.
Mechanical wave
- Sound is a mechanical wave because it is a vibration that must travel through a material medium such as air, water, or solids and cannot propagate through a vacuum.
- The vibrating source (like a speaker or tuning fork) makes nearby particles oscillate and pass energy along, which is the hallmark of a mechanical wave.
Longitudinal/pressure wave
- In a typical medium like air, sound is a longitudinal wave, meaning the particles of the medium vibrate back and forth parallel to the direction the wave travels.
- This back‑and‑forth motion creates regions of compression and rarefaction, so sound in fluids is also described as a pressure wave.