Richard F. Keltie
Ctr. for Sound and Vib., Dept. of Mech. and Aerospace Eng., Box 7910, North Carolina State Univ., Raleigh, NC 27695
This study examined the used of a compliant coating on a plate to attenuate the transmitted structure-borne sound at the interface between the coating and the ambient acoustic medium. In order to gain physical insight into the problem, the layer was modeled as a fluid with dissipation. Although realistic layers are likely to be visco-elastic materials, the fluid layer approach has been used to provide for a tractable and useful analytical model. The performance of the layer model was evaluated by calculating the displacement field at the layer/medium interface in response to structural excitation. The 3-D wave-number-frequency response amplitude spectrum of the dynamic compliance was examined. This provided for the identification of the dominant processes determining the layer response. A simple physical interpretation of these results was shown to involve the dispersive characteristics of plate waves and acoustic waveguides. It was shown that the structural effects of the plate could be eliminated from the analysis, resulting in a model involving only the layer itself. The subsequent performance of the layer as a displacement (or velocity or acceleration) attenuator or amplifier was then examined. [Work supported in part by Naval Undersea Warfare Center, New London, CT.]