IMPROVEMENT OF A HIGH-FREQUENCY BROADBAND ENERGY-INTENSITY BOUNDARY ELEMENT METHOD TO INCLUDE HIGH RESOLUTION SPECULAR REFLECTION

Abstract

The prediction of the spatial mean-square pressure distribution within enclosed high-frequency broadband sound fields is computationally intensive if determined on a frequency-by-frequency basis. Recently an energy-intensity boundary element method (EIBEM) has been formally developed. This method employs uncorrelated broadband directional energy sources to expeditiously predict such pressure distributions. The source directivity accounts for local correlation effects and specular reflection. The method is applicable to high modal density fields, but not restricted to the usual low-absorption, diffuse, and quasi-uniform assumptions. The approach can accommodate fully specular reflection, or any combination of diffuse and specular reflection. This boundary element method differs from the classical version in that element size is large compared to an acoustic wavelength and equations are not solved on a frequency-by-frequency basis. In the earlier EIBEM, the source strength and directivity associated with the energy sources, distributed over enclosure boundaries, were determined in an iterative manner and the directivity was limited to three terms of a Fourier expansion. Here, the original method is improved by eliminating the iteration and allowing for an unlimited number of terms in the Fourier expansion of the directivity function. For verification, the improved EIBEM is compared to experimental measurements and exact analytical solutions; excellent agreement is obtained.