Inverse acoustic characterization of rigid frame porous materials from impedance tube measurements

摘要

This paper presents a method for the inverse characterization of rigid frame porous materials using audible frequency acoustic measurements in an impedance tube. The characterizing parameters are the six acoustical parameters in the Johnson-Lafarge model. The proposed method is based on a minimization process, where the quantities of interest are found as the minimizing values for the difference between measured and modelled density and compressibility. Measurements are performed in an impedance tube and a scattering matrix formulation is used to obtain the reflection and transmission coefficients R and T, found as the elements of the scattering matrix, and to obtain the effective density and compressibility. Five different porous materials are tested and the results of the inversion process are compared to direct measurements of the acoustical quantities as well as to an already established recovery method [Panneton&Olny, JASA 2006]; [Olny&Panneton, JASA 2008]. The results are also validated against measurements with a rigid backing. It is found that the current method can be used to recover the material parameters quickly and reliably.