Measurement and projection of acoustic fields

The 3-D reconstruction of an acoustic field provides extensive information which can be applied to the study of radiation and scattering problems, and the information obtained provides a comprehensive analysis of the acoustic vibrator under study. Emphasis is mainly on the inverse aspects of the problem, that is, the backwards propagation of the pressure field from the measurement contour to the surface of the source. A survey of the various approaches which allow the extension of measured data into three dimensions is given. In the simplest approaches, the 2-D measurement contour is planar or cylindrical, best suited for vibrators which conform closely to these geometries. The measurement contour can be generalised to arbitrarily shaped bodies, expanding considerably the types of sources which can be studied with near-field acoustic holography techniques