Evaluation of Nonlinear Impedance Models for Acoustic Liners Under the Normal Incident Sound Wave

In this study, impedances for five specimens of the acoustic liner are measured by two methods under white noise and pure tone with a Normal Incidence Tube (NIT). Next, four nonlinear impedance models are analyzed and compared with the experimental results. Finaly, the flow resistivity used in the liner specimens are measured and compared with the results of analytical models. It was found that resistance is affected by Sound Pressure Level (SPL), whereas reactance is less affected by SPL and that compared to the experimental results. The results of Maa and Laly et al models were found to be in close agreement with the experimental results, although there were some discrepancies. It is supposed that analytical flow resistivity should be modified used in Laly et al for better estimation.