A general method is presented that allows for the inverse identification of the intrinsic properties of multi-layer porous materials in an impedance tube. To avoid the inverse problem ill-posedness, different air-gaps are placed behind the materials, artificially increasing the information contained within the observed signals. A Bayesian representation of knowledge is taken, where information on a material property is encoded in a probability density function. A numerical case with known material properties is shown as an example for the identification of a three-layer material.