Localization and Contribution of Underwater Acoustical Sources of a Moving Surface Ship

With the advent of new standards for the regulation of acoustic radiation from ships, the measurement of the underwater acoustical radiation of surface ships has become a new concern. This paper proposes array signal-processing methods for loca-lization and estimation of the spectral contributions of underwater acoustic-noise sources of moving surface ships. Beamforming for moving sources is used for localization of the acoustic-noise sources. Then, deconvolution of the point-spread function in the beamforming is performed to estimate the noise-source contributions in this underwater application. Among the classical methods of deconvolution in an aerial environment, the source density modeling method is chosen. However, weighting of the beamforming for moving sources is not adapted to the study of large vessels such as ships, which induces the localization of nonphysical sources. A new beamforming weighting strategy is proposed to deal with this issue. In addition, as beamforming for moving sources suffers from poor resolution at low frequencies, a passive synthetic aperture array algorithm is proposed here to successfully improve the resolution. A unique experiment was performed to validate the proposed methods, on Castillon Lake, Alpes-de-Haute-Provence, France, with a towed surface ship and controlled noise sources. In these experiments, the localization performance of the beamforming for moving sources is improved by the synthetic aperture algorithm. Moreover, the new weighting strategy provides better estimation of the contribution of the sources from the deconvolution results.