Boundary element method for the acoustic characterization of a machine in bounded noisy environment

In this article, a boundary element method is used to recover free field conditions from noisy bounded space situations. The proposed approach is based on the Helmholtz integral formulation. The method requires the knowledge of double layer pressure fields on two parallel closed surfaces surrounding the source. First, the outgoing and ingoing pressure field are separated using Helmholtz integral. Then, the incident field scattered by the tested source is subtracted from the outgoing field to recover the pressure field which would have been radiated in free space. To simplify the process, rigid body approximation for the source is used. The method is numerically tested in the following conditions: the chosen sound source is the upper spherical cap of a rigid sphere, the source is located at the center of a rigid spherical cavity, and a monopole secondary source is added to blur the primary pressure field. Simulations give good results for ka up to 5 when the discretization of the surfaces is sufficient.