A discrimination and measurement method of ship-radiated noise using a small aperture cylinder array based on super-directivity

A novel method of discriminating among the noise sources and measuring the ship-radiated noise levels via a super-directivity small aperture cylinder array is proposed; this is used to eliminate the effect caused by the acoustic channel and to solve the problem that it is difficult to place the measurement array. The narrow beamwidth and high gain can be obtained with optimal weighting technology to distinguish among the sources and to estimate the source levels. In this method, firstly, the beamforming theoretical model of the super-directivity cylinder array is established. Then, the calculation formula for measuring the ship-radiated noise based on the super-directivity small aperture cylinder array is derived. Finally, the resolution of the ship-radiated noise sources and measurement performance are, respectively, analyzed in the simulation and the results and their analysis demonstrate preliminarily that, when the ratio of the inter-element spacing to the wavelength is less than 0.5: (1) the directivity index obtained with the proposed method is greater than that obtained with conventional beamforming, and it is effective to use the proposed method to discriminate among the sources; (2) in the low frequency band of the ship-radiated noise, the effectiveness of the proposed method is verified, and the measurement error can be significantly reduced.