Bayesian inversion from Sabine absorption coefficients to flow resistivity values for porous absorbers

The Sabine absorption coefficient, as the equivalent absorption coefficient of a test specimen in a reverberation chamber based on two reverberation time sets with and without an absorber specimen according to ISO 354, has several problems. The most prominent problem is that the Sabine absorption coefficient of an identical specimen varies largely with the test reverberation chamber where it is measured. Therefore, the measured quantity is regarded as a combination of the true absorption characteristic of the specimen and a factor exclusively added by the room. In this study, a Bayesian framework to determine the flow resistivity of a porous material from the Sabine absorption coefficient was investigated through a reliable model. The model for the flow resistivity estimation is based on an equivalent fluid model, i.e., Miki's model, together with the most advanced model that accounts for edge diffraction, named Thomasson's finite size correction. As input data, a set of the Sabine absorption coefficients in a recent absorption round robin test in 13 European chambers was used. Finally, the flow resistivity of the test specimen is characterized via the Bayesian framework, together with the individual room factor of the reverberation chamber.