A method for computing the sound power of machines

Abstract

In this paper, a computational method for assessing the sound power characteristics of machines is presented. The method, which is based upon a Helmholtz integral formulation, requires a knowledge of the geometry and the modal characteristics of a machine's vibrating surfaces. Closed form integration of the associated surface integral is carried out in a piecewise manner over planar surface elements of simple shapes such as rectangles and triangles. This choice of element allows the grid geometries associated with the acoustic power computations to be made identical to those used in existing structural modal analysis schemes such as finite element methods or Fourier analysis methods. In this way, the sound power characteristics of a given machine can be computed in terms of the sound power radiated by each of the structural modes comprising the overall response. The structural modes can then be ranked in order of their radiation efficiency for purposes of noise control treatments.