**Sound energy density** or **sound density** is the sound energy per unit volume. The SI unit of sound energy density is the pascal (Pa), that is the joule per cubic metre (J/m^{3}) in SI based units.

Sound energy density, denoted *w*, is defined by

w
=
p
v
c
where

*p* is the sound pressure;
*v* is the particle velocity in the direction of propagation;
*c* is the speed of sound.
The terms instantaneous energy density, maximum energy density, and peak energy density have meanings analogous to the related terms used for sound pressure. In speaking of average energy density, it is necessary to distinguish between the space average (at a given instant) and the time average (at a given point).