Nonlinear acoustic properties of perforated liners: New theory and experiment
Keywords:Experiments, Transfer matrix method, Acoustic mass, Experimental investigations, Geometric parameter, New theory, Non-linear model, Nonlinear impedance, Single degree of freedoms, Sound absorber
AbstractA new nonlinear impedance model of a micro-perforated panel (MPP) is developed using an equivalent fluid concept, which is relatively easy to integrate into the Transfer Matrix Method (TMM) to predict performance of multiple MPP sound absorbers. The nonlinear model is proposed to change the linear-end correction of the acoustic mass in terms of tortuosity. The proposed nonlinear equivalent tortuosity is given by nonlinear end correction. It is found that the effect of the vibration of the air particles on the baffle in the vicinity of the aperture increases the thermo-viscous frictions. As a first validation of the model, an experimental investigation of the linear and nonlinear impedance of single degree of freedom 1 DOF and 2DOF MMP based liners are used with different type of geometric parameter. A good agreement is found between the model and the experiments for the reactance part. This confirms the correction of the radiation part of the present model.
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