A technique for the computation of sound radiation by vibrating bodies using multipole substitute sources

An existing simple engineering approach for the identification of monopole substitute sources used for sound radiation prediction is further extended to multipole sources using the concept of a discrete multipole. Such a multipole is represented by a cluster of closely spaced monopoles. Once the multipole geometry is selected, the identification of their positions and strengths is done by an appropriate computation. The identification of the positions of the substitute sources is based on an iterative search technique. It consists in scanning a grid of candidate source positions and selecting the optimally placed ones by a search loop aimed at minimising the difference of normal velocities produced by the original and substitute sources. It has been found that, given the total source capacity (the product of the source number and source order) multipoles perform better than monopoles as substitute sources, especially at high wavenumbers. The accuracy of results is sensitive to the grid spacing between candidate points which should not exceed half the wavelength.