Determining the characteristic impedance across a wide frequency range using a three-microphone impedance tube measurement

In acoustical materials research, characteristic impedance is one essential function for evaluating materials' performance. Multiple models have been developed for the characteristic impedance of porous materials. However, few studies have discussed the performance of these models at high frequencies. This work compares the effectiveness of characteristic impedance models in an extended frequency range. The three-microphone method is used for measuring characteristic impedance and propagation coefficients [Salissou & Panneton, J. Acoust. Soc. Am. 128, pp. 2868-2876 (2010)]. Multiple impulse responses measured at different circular positions are averaged to achieve an extended frequency range. Validation of the extended frequency characterization is achieved through an empty impedance tube measurement with a theoretical air layer. Bayesian inference is applied to estimate key parameters in characteristic impedance models. Porous materials are analyzed using some popular characteristic impedance models.