Analysis of vibrating structures in nonlinear media using the extended angular spectrum method

A measurement technique capable of remotely determining the characteristics of vibrating structures is described. The technique may be used to predict a particle velocity field distribution over a plane, based upon a known field contour at a parallel plane. The restriction to planar distributions does not significantly limit the applicability of the technique because many practical sources can be modelled as planar radiators with characteristic phase distributions. The technique allows the reconstruction of cross-sectional images of the particle velocity field radiated by a vibrating structure. Reconstructions are generated by applying a propagation algorithm to measured or simulated planar particle velocity distributions. The authors outline the basic principles and further development of the algorithm often referred to as the angular spectrum method. Selected results which demonstrate the ability of the angular spectrum method to analyze vibrational characteristics and accurately predict the propagation of acoustic fields are presented. The applicability of the method is also discussed based upon comparisons between experimental data and extended angular spectrum predictions