Sound power or acoustic power $P_a$ is a measure of sonic energy $E$ per time $t$ unit. It is measured in watts and can be computed as sound intensity ($I$) times area ($A$).
Applicable units are those of quantitykind:Power
http://en.wikipedia.org/wiki/Sound_power
$P_a = IA$, where $I$ is the sound intensity in $\frac{W}{m^2}$ and $A$ is the area in $m^2$.