Effect of internal mass isolation on the radiated sound power of a submerged hull

The primary aim of machinery isolation in submarines is to isolate structural vibration of the onboard machinery from the hull and to reduce far-field radiation of noise from the submarine. The isolation system can also be used to protect sensitive components from underwater explosions. A substantial proportion of the total submarine mass is on flexible mounts that isolate supported masses from the hull at frequencies above the mounting system resonant frequency. This reduces the dynamically effective mass of the hull and affects the signature of the submarine due to propeller excitation. A fully coupled finite element/boundary element (FE/BE) model has been developed to investigate the effect of system isolation in a submarine hull. The finite element model of the structure includes internal structures to represent the machinery and other flexibly mounted components. Sound power plots demonstrate the effect of machinery isolation on the acoustic signature of a submarine due to excitation from its propeller.