Researches on the measurement of distribution image of radiated noise using focused beamforming

A method using focused beamforming to measure the distribution image(under- water image)of submarine and surface ship's noise sources is presented.Level linear array can measure the target image on water level,but the multi-path interference of underwater acoustic channel may affect the quality of it.Virtual time reversal mirror and virtual array can both solve the problem very well;they make the image with high resolution.