Reduction of noise radiated from ship structures

Abstract The noise power generated by a normal point force excitation applied to various types of ships' hulls are compared with theoretical values for an infinite plate. Tests simulating the response of a hull structure by vibrating one panel of a box floating in a tank of water and measuring the transmitted noise power are described. The effect of applying a damping treatment and various types of external compliant coatings to the panel are measured, as well as the corresponding changes of mechanical impedance at the point of application of the force input to the plate. In addition information is given on the variation of noise vibration levels with distance from a noise source. Experiments to determine this on both hull and superstructures are described, and the effects of radiation to the water and of airborne noise absorption treatments are measured. The importance of vibration as a flanking path in airborne noise insulation is discussed, and the reduction of airborne noise transmitted through panels damped by friction is given.