Viscoelastic Materials for Noise Reduction on Board

complex paths that can often include conversions from an acoustic form of energy into a mechanical one and vice-versa. The present work reviews the physical concepts at the basis of counter-measures adopted on noise transmission paths on board and analyses the physical quantities that can be used to quantify their effectiveness. The work concentrates on a particular type of noise counter-measure, nowadays widely used in the shipbuilding industry: the adoption of damping layers on the intermediate and final part of the transmission paths. The adoption of viscoelastic materials applied in a constrained layer arrangement is discussed in particular. A description is presented of a simplified procedure for comparative tests of different viscoelastic materials and of different configurations. Results are included, regarding damping layers applied to steel and GRP structures.