Boundary element analysis of the sound field around a vibrating box. (Sound radiation from a vibrating gear box. 1st report)

Abstract

Three dimensional sound fields described by the exterior Neumann problem of the Helmholtz equation are formulated. Application of the boundary element method to this problem is presented. Combined Helmholtz integral equation formulation (CHIEF) is adopted to overcome the numerical difficulty due to the non-unique solution at the eigenfrequencies of the associated interior Dirichlet problem. Numerical accuracies by the present method are examined with the cubic model circumscribed about a uniformly vibrating sphere. Sound fields radiated from a box with one or two vibrating faces are calculated and compared with ones measured in a nearly anechoic room. Results show that the effects of diffraction and interference on the sound fields are well predicted. Distributions of sound intensity level are also simulated.