Estimation of all six parameters of Johnson-Champoux-Allard-Lafarge model for acoustical porous materials from impedance tube measurements.

Abstract

The open porosity of air-saturated acoustical porous materials is estimated from the low-frequency or high-frequency asymptotes of the real part of the dynamic bulk modulus. Combining this technique with the estimation of the static air-flow resistivity from the low-frequency asymptote of the imaginary part of the dynamic mass density and the analytical inversions of the remaining parameters from the dynamic mass density and bulk modulus [methods introduced by Panneton and Olny, J. Acoust. Soc. Am. 119(4), 2027-2040 (2006) and Olny and Panneton 123(2), 814-824 (2008)], this work estimates all six parameters of a Johnson-Champoux-Allard-Lafarge model from impedance tube measurements. A classical two-microphone impedance tube, as well as three- or four-microphone tubes, can be used for these measurements and estimations. Examples of applications and limits of the method are presented and a tool to estimate the open porosity and the static air-flow resistivity is made available online.