Sound energy flux

The sound energy q results from the integral particle velocity v of the surface  A , whereby only the portions perpendicularly to the surface acoustic velocity are important.

q = \int \overrightarrow{v} \, \overrightarrow{\mathrm{d}A} $$

The sound energy flux marks the volume of the transmitting medium (air), which - caused by the excess sound pressure - and flows per time unit (1 s) by a surface A.

The sound energy flux is the average rate of flow of sound energy for one period through any specified area.

In a medium of density ρ for a plane or spherical free wave having a velocity of propagation v, the sound energy flux through the area A corresponding to an effective sound pressure p is


 * J = (p2A / ρ v) cos θ

where θ = the angle between the direction of propagation of the sound and the normal to the area A.

Schallfluss