Piezocomposite SmartFoam for Active Control of Underwater Noise

A study on smart foam for passive-active underwater sound reduction in sound pulse tube is presented. The smart foam consists of cylindrically curved sections of PVDF film embedded in polyurethane acoustic foam forming a thin, compact arrangement. The device is designed to reduce sound by the simultaneous action of the passive absorption of the foam (effective at high frequencies) and the active input of the PVDF element driven by an oscillating electrical input(effective at low frequencies). A digital time delay & feed-forward control system has been developed and severs for the smart foam control system. The concept of smart foam control system is that of an open-loop velocity feedback between sensors and actuator.