Sound power

Sound measurements

Sound power or acoustic power "P"_ac is a measure of sonic energy "E" per time "t" unit.

It is measured in watts, or sound intensity "I" times area "A"::$P\_\{mathrm\{acoustic\; =\; I\; cdot\; A$

The measure of a ratio of two sound powers is:$L\_mathrm\{w\}=10,\; log\_\{10\}left(frac\{P\_1\}\{P\_0\}\; ight)\; mathrm\{dB\}$

where:"P"₁, "P"₀ are the sound powers.

The sound power level PWL, L_W, or L_Pac of a source is expressed in decibels (dB) and is equal to 10 times the logarithm to the base 10 of the ratio of the sound power of the source to a reference sound power. It is thus a logarithmic measure.

The reference sound power in air is normally taken to be 10⁻¹² watt = 0 dB SWL.

Sound power is neither room dependent nor distance dependent. Sound power belongs strictly to the sound source.

Table: Sound power and sound power level of some sound sources

:

Usable music sound (trumpet) and noise sound (excavator) both have the same sound power of 0.3 watts, but will be judged psychoacoustically to be different levels.

ound power with plain sound waves

Between sound power and other important acoustic values there is the following relationship:

$P\_\{ak\}\; =\; xi^2\; cdot\; omega^2\; cdot\; Z\; cdot\; A\; =\; v^2\; cdot\; Z\; cdot\; A\; =\; frac\{a^2\; cdot\; Z\; cdot\; A\}\{omega^2\}\; =\; frac\{p^2\; cdot\; A\}\{Z\}\; =\; E\; cdot\; c\; cdot\; A\; =\; I\; cdot\; A$

where:

External links

* [http://www.sengpielaudio.com/calculator-ak-ohm.htm Ohm's law as acoustic equivalent — calculations]
* [http://www.sengpielaudio.com/RelationshipsOfAcousticQuantities.pdf Relationships of acoustic quantities associated with a plane progressive acoustic sound wave — pdf]