Editing Particle velocity (section)

{{short description|Velocity of a particle in a medium as it transmits a wave}}
{{Sound measurements}}

'''Particle velocity''' (denoted {{mvar|v}} or {{math|SVL}}) is the [[velocity]] of a [[particle]] (real or imagined) in a [[Transmission medium|medium]] as it transmits a [[wave]]. The [[International System of Units|SI unit]] of particle velocity is the metre per second (m/s). In many cases this is a [[longitudinal wave]] of [[pressure]] as with [[sound]], but it can also be a [[transverse wave]] as with the vibration of a taut string.

When applied to a sound wave through a medium of a fluid like air, particle velocity would be the physical speed of a [[Fluid parcel|parcel of fluid]] as it moves back and forth in the direction the sound wave is travelling as it passes.

Particle velocity should not be confused with the speed of the [[wave]] as it passes through the medium, i.e. in the case of a sound wave, particle velocity is not the same as the [[speed of sound]]. The wave moves relatively fast, while the particles oscillate around their original position with a relatively small particle velocity. Particle velocity should also not be confused with the velocity of individual molecules, [[Kinetic theory of gases#Speed of molecules|which depends mostly on the temperature and molecular mass]].

In applications involving sound, the particle velocity is usually measured using a logarithmic [[decibel]] scale called [[particle velocity level]]. Mostly pressure sensors (microphones) are used to measure sound pressure which is then propagated to the velocity field using [[Green's function]].