Sound energy density
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| Sound measurements | |
|---|---|
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Characteristic
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Symbols
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| 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 |
|
|
|
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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/m3) in SI based units.
Contents
Mathematical definition
Sound energy density, denoted w, is defined by
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).
Relationships with other quantities
Sound energy density is related to sound intensity:
where
- I is the sound intensity;
- c is the speed of sound.
Sound energy density is related sound power:
where
- P is the sound power;
- A is the area.
