Passive and active control of the radiated sound power from a submarine excited by propeller forces

To improve the stealth of a submarine, the sound power radiated from the hull can be reduced using active noise and vibration control. In this article, active control is applied to minimize hull excitation by propeller forces transmitted through the shaft. The dominant propeller axial force fluctuations are directly related to blade passage and the phase of the force is determined by the absolute angle of the propeller shaft. Because the propeller forces are deterministic, the application of feedforward control is appropriate. Numerical finite element/boundary element (FE/BE) models of a submarine have been developed to find the transfer functions. Different control strategies are investigated in which active control is applied to the propeller/shafting system and/or to the submarine hull. Active vibration control and discrete structural acoustic sensing based on the far-field radiated sound power were considered for development of the cost function. In addition, the performance of a system in which active control is combined with passive control using a resonance changer is investigated. It is shown that the combination of tuned control actuators and a resonance changer results in a significant reduction of radiated sound power.