Energetic sound propagation in rooms

For most practical purposes in room acoustics it is sufficient to restrict sound field calculations to the propagation of sound energy. In this paper, an energetic approach to sound field calculation is presented which is based on a simple integral equation. It allows the calculation of the energy density and the sound intensity, both steady state and transient. Furthermore, the decay time of an enclosure can be obtained by a simple iteration scheme, the inverse problem (calculation of absorption coefficient from given reverberation time) can be solved in a similar way. The methods are illustrated by simple examples.