抄録
A numerical method is proposed to calculate damping properties for sound-proof structures involving solid body,porus media and air in three dimensional regions. Both effective density and bulk modulus have complex quantities to represent damped sound fields in the porous media.Particle displacements in the media are discretised using finite element method.For solid body, displacements are modeled using conventional finite elements including complex modulus of elasiticity.Displacement vectors at common unknown variables,are solved under coupled condition between solid body,porous media and air. Further,expressions of modal loss factor for the mixed structures are derived using asymptotic method. Using this expression,damping properties are analyzed for a panel with porous media.The bottom of this panel is supported by porous media and the top of the panael is faced to a closed space.Further,thickness of porous media layer and air layer are varied.It is analyzed that the influence of the porus media and air layer thickness and vibration mode upon damping properties.
