Sound energy density

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Sound quantities

The sound energy density (symbol E or w ) is a measure to describe the sound energy present at a certain location in the sound field . It is a sound energy quantity . The associated logarithmic quantity is the sound energy density level.


The sound energy density  E is the sound energy per volume unit:

It gives information about the sound energy  W at a certain location of a sound field and is its energy density .

The unit of sound energy density is joules per cubic meter  (J / m³).

In the special case of the even advancing wave, the time-averaged sound energy density is:


where I is the sound intensity and c is the speed of sound .

Sound energy density level

Occasionally the sound energy density is also given in the form of a sound energy density level L E in decibels  (dB):

The reference value is defined as J / m³ or W · s / m³.

Relationships in the plane wave

Further formulas for the sound energy density for flat, progressing sound waves:


symbol units meaning
E. W · s / m 3 Sound energy density
ξ m , meter Sound deflection
= 2 · · f rad / s Angular frequency
ρ kg / m 3 Air density , density of the air (of the medium)
v m / s Speed ​​of sound
a m / s 2 Sound acceleration
p Pascal Sound pressure
f hertz frequency
Z = c ρ N · s / m 3 Characteristic acoustic impedance, acoustic field impedance
I. W / m 2 Sound intensity
c m / s Speed ​​of sound
P ak W, watt Sound power
A. m 2 Transmitted surface

Web links

Individual evidence

  1. DIN 1320: Acoustics: Terms . Edition 1997-06.