# Sound energy

Sound measurements
Characteristic
Symbols
Sound pressure  p, SPL
Particle velocity  v, SVL
Particle displacement  δ
Sound intensity  I, SIL
Sound power  P, SWL, LWA
Sound energy  W
Sound energy density  w
Sound exposure  E, SEL
Acoustic impedance  Z
Speed of sound  c
Audio frequency  AF
Transmission loss  TL

Sound energy is a form of energy associated with the vibration of matter. The SI unit of sound energy is the joule (J). Sound is a mechanical wave and as such consists physically in oscillatory elastic compression and in oscillatory displacement of a fluid. Therefore, the medium acts as storage for both potential and kinetic energy as well.[1]

Consequently, the sound energy in a volume of interest is defined as the sum of the potential and kinetic energy densities integrated over that volume:

${\displaystyle W=W_{\mathrm {potential} }+W_{\mathrm {kinetic} }=\int _{V}{\frac {p^{2}}{2\rho _{0}c^{2}}}\,\mathrm {d} V+\int _{V}{\frac {\rho v^{2}}{2}}\,\mathrm {d} V,}$

where