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
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.

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:

$W = W_\mathrm{potential} + W_\mathrm{kinetic} = \int_V \frac{p^2}{2 \rho_0 c^2}\, \mathrm{d}V + \int_V \frac{\rho v^2}{2}\, \mathrm{d}V,$

where

• V is the volume of interest;
• p is the sound pressure;
• v is the particle velocity;
• ρ₀ is the density of the medium without sound present;
• ρ is the local density of the medium;
• c is the speed of sound.

See also

• Sound energy density level