Acoustic Radiation from an Automotive Gear Box

The main goal of this paper is to extend the acoustic boundary element analysis to the high frequency regime. At higher frequencies, the surface boundary element mesh of the radiator must be sufficiently fine to capture the rapid spatial variations of the sound field. Traditional BEM implementations have had difficulty in dealing with large number of unknown variables and thus are limited to low frequency analysis of small bodies. In a typical boundary element analysis, computation of the coefficient matrix constitutes a major portion of the total analysis time and total memory usage.

The key to obtaining rapid solutions of large problems using BEM is to completely bypass the coefficient matrix computation. We have developed a new Direct Boundary Element Variational formulation that is used in conjunction with iterative solvers from the Krylov family, and a new Multilevel Fast Multipole Method (MLFMM) that facilitates extremely fast matrix-vector product computation. This approach overcomes the limitations of traditional BEM and allows us to perform fast NVH analysis of large problems in the mid-high frequency regime. We demonstrate the accuracy of our predictions by comparing with several closed form analytical solutions. Noise radiated by a gear box housing was analyzed as an example automotive NVH application.