Further exploration of characteristic impedance measurement at extended frequency range

Characteristic impedance is often used in the acoustical material community to evaluate the performance of materials. The characteristic impedance of the porous material is measured using the three-microphone method with multiple microphones along the circumference. Circumferential modes are canceled with the method, and given the tube diameter the cutoff frequency is extended to twice that of the traditional three-microphone impedance tube measurement. Further challenge in the characteristic impedance measurement is explored and discussed in this work. The critical parameters of the testing material are estimated through Bayesian analysis.