# Sound energy

Sound measurements
Characteristic
Symbol
Sound pressure  p · SPL
Particle velocity  v · SVL
Particle displacement  ξ
Sound intensity  I · SIL
Sound power  Pac
Sound power level  SWL
Sound energy
Sound exposure  E
Sound exposure level  SEL
Sound energy density  E
Sound energy flux  q
Acoustic impedance  Z
Speed of sound
Audio frequency  AF

Form of energy associated with the vibration or disturbance of matter. Sound is a mechanical wave and as such requires a medium to travel through.

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

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

With

• $V$ – the volume, or region of 3-space, of interest
• $p$sound pressure
• $v$particle velocity
• $\rho_0$density of the medium without sound present
• $\rho$ – local density of the medium
• $c$sound speed