Nearfield acoustic holography: Review and perspectives

The development of the Nearfield Acoustic Holography technique (NAH) for planar arrays is reported. A critical review shows that this technique represents an improvement over standard Acoustic Holography (AH) only for reconstructions of sources radiating at low frequencies. The possible reasons for a bad source reconstruction in NAH are investigated. The sensitive parameters for producing this distortion in a given system are detected. It is shown that the aliasing of the signal requires a formal approach or research. This formal approach is necessary for generalizing the technique, and for avoiding the subjectivity in choosing a good reconstruction. The results lead to the conclusion that prior knowledge of the source under study is required, making NAH a case-by-case method. The choosing of the true solution appears to be a time consuming technique from just a mathematical approach, or a highly subjective technique if there is not a formal approach. At the present state of development, NAH can only work in some cases. A system for industrial applications does not seem a real possibility at the present time.