Lightweight porous materials such as polyurethane foams, mineral wools, fibrous foams and lightweight glass are extensively used as noise control materials in many applications. The performance of porous media depends on microscopic structure which controls macroscopic material properties. The macroscopic physical material properties together with geometric properties and boundary conditions determine the acoustical performance. The relationship between the material, geometric properties and acoustical performance is governed by modified Biot's theory.

Typically, the solution of equations based on Biot’s theory in arbitrary configurations and boundary conditions requires the use of numerical methods such as finite and boundary element methods. On the other hand, performance of planar multi-layer treatments can be evaluated analytically using transfer matrix methods or four-pole method.Additionally, the relationship between the properties and performance can be used to estimate the material properties from measured performance metrics such as transmission loss and/or absorption coefficient.The performance metrics can be measured relatively easily using readily available impedance tubes.

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