Sound energy density
|Sound pressure||p · SPL|
|Particle velocity||v · SVL|
|Sound intensity||I · SIL|
|Sound power level||SWL|
|Sound exposure level||SEL|
|Sound energy density||E|
|Sound energy flux||q|
|Speed of sound|
The sound energy density or sound density (symbol E or w) is an adequate measure to describe the sound field at a given point as a sound energy value. The letter "lower case w" sign is easily mixed with the sign (omega), therefore we choose the letter E.
In opposite to the sound intensity I, which gives the sound power per area A, the sound energy density E (also: sound density) describes the time medium value of the sound energy per volume unit; it gives information about the sound energy which is at a defined place in the room.
The sound energy density E (or w) for an even-proceeding sound wave is:
where I is the sound intensity in W/m2 and c is the sound speed in m/s.
The sound energy density is given in J/m3, where the joule J = W·s = N·m.
You will find also W·s/m3 or N·m/m3.
The unit of measurement for sound energy density is N/m2, also known as pascals, the same as the units of sound pressure.
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).
More formulas for sound energy density for even proceeding sound waves:
|ξ||m, meters||particle displacement|
|c||m/s||speed of sound|
|= 2 · · f||radians/s||angular frequency|
|ρ||kg/m3||density of air|
|Z = c · ρ||N·s/m³||acoustic impedance|
|E||W·s/m³||sound energy density|
|Pac||W, watts||sound power or acoustic power|