An advanced noise source identification technique using the inverse boundary-element method

Abstract

The application of the inverse BEM method as an advanced, non-contact noise source identification technique will be discussed. In the first and most conventional experiment, the inverse BEM is used to reconstruct the vibration pattern on the surface of a motorcycle engine oil pan cover. In the second experiment, the inverse BEM is used to determine the distribution of particle velocity on the open end of a rectangular duct. Measurements of the particle velocity using the two-microphone method are compared to those predicted using the inverse BEM. In the third experiment, the inverse BEM is used to identify the mechanism of an aeroacoustics noise problem (a vortex tone) created by flow over a circular rod. The spectrum of the tonal sound within the flow field is reconstructed using the inverse BEM, and a near field spatial reconstruction of the sound pressure shows clearly the nature of the vortex source. This paper will also show that only a relatively small number sound pressure measurements are required for the inverse BEM and that these measurements need not be in the near field of the source nor conformal to it to obtain good results.