A Non-Singular Boundary Integral Equation for Acoustic Problems

On the Accuracy of Nearfield Pressure Predicted by the Acoustic Boundary Element Method

“…In the close near"eld, where the distance z from the source surface is shorter than about 20% of the characteristic length, the "eld pressure predicted by CBEM has large errors (see "gures in reference [1]). Although the reason for near"eld inaccuracy has been simply ascribed to the short distance between "eld points and the source surface, further detailed explanation in needed for this phenomenon.…”

“…When a "eld point is placed in the very close near"eld to the source surface, R becomes very small and thus an instability problem will arise in the numerical integration. This problem can be solved by adopting the non-singular boundary element method (NBEM) [1]. In this method, all singularities involved in the conventional BIE can be eliminated by subtracting two propagating plane wave components from the integral identity.…”

“…A pulsating sphere and a parallelepiped cavity are employed for illustrating the near"eld accuracy of "eld properties and the guidelines for precise prediction are given as a result. All formulations for CBEM and NBEM calculation are based on those in reference [1].…”