To enhance the low frequency sound absorption of acoustic liners,mechanical impedance is introduced to the acoustic liners,and the corresponding acoustic impedance model is established and analyzed.The transfer matrix method is adopted to model the one-dimensional sound propagation.The acoustic compatibility conditions for perforated panels and mechanical impedance panels are further introduced to model the impedance of acoustic liners under the grazing flow.The re-liability of the proposed method is verified by comparing the results with those of existing literature and finite element meth-od.Numerical study concerning a 2-DOF acoustic liner with mechanical impedance is carried out and shows that the sound absorption is firstly enhanced and then weakened with the increase of the Mach number,low frequency sound absorption is enhanced by a relatively small mass of the mechanical impedance,the frequency of the sound absorption peak increases with the increase of the natural frequency of the mechanical impedance,the height of the sound absorption peak decreases with the increase of the damping of the mechanical impedance.
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