Experimental Verification of Underwater Noise Localization Based on Cylindrical Near-field Acoustic Holography

To improve the stealthiness of underwater vehicles, or reduce impacts of vessels on the marine environment, it is necessary to identify their noise sources. Furthermore, the proper acoustic control and management of underwater noise radiation of vessels is critical during the intended upgrades and operational service. Near-field acoustic holography (NAH) is a technology that acquires sound pressure in the vicinity of the hull, which can be back-propagated to locate the hot-spot on the hull and forward-propagated to predict the far-field radiated noise of the vessel. With OROS Underwater Holography software, which is the only underwater NAH solution in the market, the use of NAH for noise localization and far-field prediction will be presented through the findings from an experimental study on a large scaled model. Considering the typical shape of underwater vehicles, cylindrical NAH is adopted to provide the highest accuracy. A partial circular array consisting of 25 RESON hydrophones is placed in the vicinity of the hull to measure sound pressure. A shaker excited at random is mounted in the hull to simulate a source, whose location is known. The acoustic maps generated from the experimental measurements show good correlation between the hot-spot location and the known source location, verifying the correctness and efficiency of NAH technology in naval applications.