A numerical and experimental validation of the room acoustics diffusion theory inside long rooms

This paper focuses on the validation of the recently proposed room-acoustics diffusion theory for the propagation of sound in enclosures by means of numerical simulations and experimental measurements.\udIn particular, the analysis aims to verify the equation underlying the model (Fick’s law of diffusion), which states that the reverberant energy density gradient and the sound intensity inside a room are proportional through a constant diffusion coefficient. \udIn this work the involved acoustic quantities are numerically/experimentally derived under stationary conditions and their ratio is employed to estimate the effective value of the diffusion coefficient inside long rooms.\udThe numerical study was carried out with a set of particle-tracing simulations. The measurements were performed with a Microflown® three-dimensional sound intensity probe inside a 1:16 scale model of a long room, varying the absorption and the scattering properties at the boundaries. \udA comparison between numerical and experimental results is carried out with a least-square algorithm, showing a fair agreement between the diffusion coefficients estimated with the two methods. \udThe results lead to the conclusion that the reverberant sound field inside long rooms can be described by a non-homogeneous diffusion process: the local diffusion coefficient is not a constant inside the room but increases with the distance from the source and depends on the acoustical properties of the room boundaries