The effects of multilayer sound-absorbing treatments on the noise field inside a plate backed cavity

In this paper, a finite element approach is used to investigate the noise field inside a rigid-walled cavity coupled to a vibrating plate with a multilayer sound-absorbing treatment, The treatment is made from a combination of elastic, poroelastic, and airspace layers, The approach uses classical elastic and fluid elements to model the elastic and fluid media, For poroelastic media, it uses a two-field displacement formulation derived from the Blot theory, Furthermore, it accounts for coupling between elastic, poroelastic, and airspace layers, Numerical results illustrating several practical configurations are presented, They underline several features: the effects of the modal behavior of the structure, the nature of the poroelastic material, the effects of the damping added by the poroelastic material, the mounting configuration of the sound absorbing treatment, and finally the boundary conditions of the plate. (C) 1996 Institute of Noise Control Engineering.