On the use of poroelastic materials for the control of the sound radiated by a cavity backed plate

The purpose of this paper is to examine the potential of poroelastic materials to control the low frequency noise radiated outside a parallellepipedic cavity enclosing a point source. The enclosure consists of five rigid walls and one flexible plate, all of which may be treated with a porous slab. The Biot-Allard theory, three equivalent fluid approaches and a locally reacting assumption are used to model the porous medium. The response of the system is calculated using a finite element model for all the components. The two issues addressed are the modeling of a porous material in a complex structure and the control of the sound radiated outside the cavity. Concerning the first point, calculations confirmed the validity range of the locally reacting assumption and prove the relevance of a limp porous model for unbonded plate treatments. Regarding the second issue, the sound power reduction obtained with the treatment of nonvibrating walls is compared to that achieved when treating the plate. The efficiency of the different mounting conditions of the porous slab to the plate is also discussed. Finally, the calculation of the dissipated powers inside the system provides a crucial information to optimize the sound absorbing treatment. (c) 2006 Acoustical Society of America.