A numerical investigation of the sound intensity field in rooms by using diffusion theory and particle tracing

This work focuses on the calculation of net intensity vectors in rooms, by using two different methods: a geometrical method, based on particle tracing, and the room-acoustic diffusion theory. The classical assumption for diffuse reverberant sound fields is that the acoustic energy flow at any location in room, i.e., the acoustic intensity is null. The reverberant field in rooms with homogeneous dimensions and uniform absorption coefficients is usually considered as diffuse. This study focuses first on the spatial structure of the intensity vector field in such rooms, showing that, although the energy density variation is weak, an organized structure of energy flows can be observed throughout the room. According to the room absorption and reflection law, the deviation of the intensity field from the prediction given by diffuse sound field theory can then be significant. For such rooms, the validity of the room-acoustic diffusion theory is also assessed by numerical calculations of the true diffusion coefficient, by considering both intensity and energy density as given par the particle-tracing model. In a second part, the net intensity field in more complex rooms, such as, for example, long rooms, will be investigated in the same way. The influence of parameters, such as the absorption coefficient and reflection law of the surfaces will be considered. Some numerical calculations of the room-acoustic diffusion coefficient will also be provided, to evaluate the validity of the diffusion theory.