Nonlinear Effect of Wire Mesh Liners Subjected to High Sound Pressure Level

Abstract

A wire mesh liner possesses a better acoustic linearity to high sound pressure level (SPL) than a perforated liner, but lacks an accurate impedance model. Thus, its nonlinear effect due to high SPL is studied in this paper. A jet simulation of mesh orifices (two-dimensional slits) is conducted. It reveals that an approximation to the nonlinear loss in an existing model (“A Model for the Acoustic Impedance of Linear Suppressor Materials Bonded on Perforated Plate,” AIAA Paper 1981-1999, Oct. 1981) includes implicitly linear loss and neglects the effect of the orifice distribution uniformity, and so the nonlinearity of distributed micro-orifices is overestimated. This accords with the experimental result in an impedance tube that the high-SPL resistance is overestimated for a fine mesh. Meanwhile, it is indicated that the discharge coefficient is overestimated in the existing model for neglecting the vena contracta at least at the maximum jet of a coarse mesh, and so the high-SPL resistance is underestimated. Therefore, the nonlinear loss factor is defined herein to exclude the linear loss and avoid the deviation from the jet contracta of the mesh, which presents a better prediction. Finally, an empirical relation of considering the orifice diameter and a correction to the reactance are given experimentally, and thus, a more accurate impedance model of the wire mesh liner is established.