An acoustic porous material is a combination of a fluid phase and a solid phase. It is generally modeled using the well-known Biot theory for poroelastic materials. To account for visco-inertial and thermal dissipations, the Johnson-Champoux-Allard (JCA) model and the Johnson-Lafarge (JL) model are typically used. Depending on the model and frame type (rigid, limp, or elastic), up to 10 parameters are needed.
If frame is rigid or limp, the porous material can be modelled as an equivalent fluid having an effective dynamic density and bulk modulus (compressibility). Typical equivalent fluid models are JCA and JL.
For more information on the modeling of sound absorbing porous materials, refer to book by Allard and Atalla.
Rigid, Limp and Elastic Frames
Limp and Elastic Frames