Flow Noise Calculation and Experimental Study for Hydrophones in Fluid-Filled Towed Arrays

Understanding the physical features of the flow noise for hydrophones in a fluid-filled towed array is important for designing a towed line array sonar. The flow noise of hydrophones in fluid-filled towed arrays generated by the turbulent pressure is derived by the frequency–wave number decomposition method. The results show that the flow noise increases rapidly with the towed speed and decreases with the length of the hydrophone. Meanwhile, the flow noise is closely related to the material parameters of the elastomer tube. It decreases with the attenuation factor, outside radius, and thickness of the elastomer tube. Furthermore, a spatial filter designed by the constant sector inverse-beamforming method is used for suppressing the tow-ship-radiated noise and the ambient noise from the sensor data. The analysis results of the experimental data are consistent well with the theoretical values, which indicate that the tow-ship-radiated noise and the ambient noise are suppressed effectively by the spatial filter. In addition, the correlation features of the flow noise received by the acoustic array are analyzed, which is important for the sonar system design.