Abstract
Model tests are performed in order to predict the noise level of a full ship and to control its noise signature. Localizing noise sources in the model test is therefore an important research subject along with measuring noise levels. In this paper, a noise localization method using a hydrophone array in a large cavitation tunnel is presented. The 45-channel hydrophone array was designed using a global optimization technique for noise measurement. A set of noise experiments was performed in the KRISO (Korea Research Institute of Ships & Ocean Engineering) large cavitation tunnel using scaled models, including a ship with a single propeller, a ship with twin propellers and an underwater vehicle. The incoherent broadband processors defined based on the Bartlett and the minimum variance (MV) processors were applied to the measured data. The results of data analysis and localization are presented in the paper. Finally, it is shown that the mechanical noise, as well as the propeller noise can be successfully localized using the proposed localization method.
Highlights
In order to reduce shipping noise, the characteristics of ship noise should be understood.Localizing the noise sources in the design stage via an indirect method, such as acoustic sensing, as well as visual observation might be very helpful for this purpose.Propeller noise, which is one of the main noise sources in ships, is mainly due to its turns as spectral harmonics and to cavitation as broadband noise
In contrast to the full-scale measurements where noise components coming from other sources, such as a loud engine, are inevitably included, the measurement of noise levels generated by rotating propellers exclusively is possible in the cavitation tunnel experiments
TheExperiment sound pressure level (SPL), which is averaged using the results from the 45 channels, 3.1
Summary
In order to reduce shipping noise, the characteristics of ship noise should be understood.Localizing the noise sources in the design stage via an indirect method, such as acoustic sensing, as well as visual observation might be very helpful for this purpose.Propeller noise, which is one of the main noise sources in ships, is mainly due to its turns as spectral harmonics and to cavitation as broadband noise. Experimental studies of cavitation noise have been performed to meet various objectives, including detecting the inception and extent of cavitation, identifying noise characteristics with respect to cavitation behaviors and predicting cavitation noise levels [1,2,3,4,5,6]. In contrast to the full-scale measurements where noise components coming from other sources, such as a loud engine, are inevitably included, the measurement of noise levels generated by rotating propellers exclusively is possible in the cavitation tunnel experiments. One of the main concerns of the cavitation noise study was establishing the measuring techniques or procedures appropriate for each type of facility configuration [7,12,13,14,15,16,17]
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