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The investigation on measuring source level of Unmanned Underwater Vehicles

An Unmanned Underwater Vehicle (UUV) is mainly composed of a large number of rotating parts, such as bearings and motors. The radiated noise of an UUV is mainly caused by mechanical vibration. In order to reduce noise and provide a foundation for noise source identification, quantitative measurement of the radiated noise source level is critically required. The classic measuring method is a sea or lake experiment, but this can easily be affected by complex ocean conditions, such as wind, rain, and also by various vessels and other background noise. Besides, the test process takes too long and costs too much. Due to the complexity of lake or sea trials, in this paper, a reverberation method is proposed to measure source level spectral density of radiated noise in a non-anechoic tank. The theory of the underwater reverberation method and how to use this method on UUV measurement is studied. The source level spectral density of radiated noise of an UUV with different rotating speeds was measured by two means respectively-in a non-anechoic tank using the reverberation method; and, at sea using the traditional measuring method. A comparison of the experimental data demonstrates that the results are in good agreement, and this verifies the accuracy of the proposed reverberation method.