On DR/BEM for eigenvalue analysis of 2-D acoustics

This paper discusses the efficiency of several DR/BEM formulations and other boundary techniques for the eigenvalue extraction of two-dimensional acoustic cavities. First, the paper shows that the well-known conical radial basis functions lead to extremely ill conditioning results in cases that the height of the cone is not properly chosen. Moreover, the accuracy of other known high-degree basis functions is tested. Second, the use of Pascal's triangle is proposed as a better approximation of the inertial forces at least for the case of rectangular domains. Using Gordon's blending-function formula, a systematic procedure is proposed for the selection of the proper monomials. Third, it is shown that the aforementioned functional set can be also used to establish an alternative boundary-type method where both inertial and static terms are treated in a consistent manner. The solution quality of these formulations is investigated by calculating the eigenvalues of a rectangular and a circular acoustic cavity where analytical solutions are known.