Rouse J., Franzoni L., Bliss D.

A new method is presented for predicting the spatial variation of mean-square pressure within three-dimensional enclosures having steady-state high-frequency broadband sound fields. The enclosure boundaries are replaced by a continuous distribution of uncorrelated broadband directional sources, which provide constituent fields expressed in terms of mean-square pressure and time-average intensity variables. Boundary conditions for radiating and absorbing surfaces are recast in energy and intensity variables. Superposition of these source fields in a numerical boundary element formulation leads to the prediction of overall mean-square pressure and time-averaged intensity as a function of position. Both specular and diffuse reflection boundaries can be accommodated. In contrast to the traditional boundary element approach, this method is independent of frequency, and each element has multiple unknowns, namely the strengths of directivity harmonics. For verification, exact analytical solutions for the mean-square pressure distribution in several model problem enclosures were obtained by modal sums and frequency integration and compared to the new method. The comparisons show the method is very accurate, and it is extremely computationally efficient in comparison to classical modal and boundary element approaches. Results also show that diffuse field methods do not provide an accurate simulation for specular reflection cases.