Measurement of sound power and energy densities

The sound power density (intensity) of a sound field in a specified direction at a point is the sound power transmitted through a unit area normal to this direction. The sound energy density is the sound energy per unit volume. The conventional measurement of the sound pressure alone, except in rare instances, will not provide either the sound power density or the sound energy density. The means and uses for the measurement of sound power density and sound energy density are described. The measurements include sound absorption of room boundaries, machine noise, and the sound power density and sound energy density of sound-reproducing systems.