An impedance model for thin microperforated panels
* Presenting author
The classic model for the sound absorption of microperforated panels (MPPs) is well developed. For an ultrathin MPP, however, interaction between the air flow on both sides of the panel is not negligible, which invalidates the impedance end corrections in the classical model. In this paper, a correction length model is proposed for the transfer impedance of an ultrathin MPP. Theoretical and numerical analyses show that the impedance jumps take place within the distance less than one half of the perforation radius. Provided that the panel thickness is larger than the perforation radius, contribution from the end effect can be well approximated by adding 1.2 times of the radius to the thickness. Sound induced vibration also significantly affects the MPP’s impedance. Herein averaged air velocity within a circular perforation is solved under the non-slip boundary condition exerted by the panel vibration velocity. Together with the flow continuity at the panel surface in a spatially mean sense, the overall acoustic impedance of the MPP is derived. The experimental results for two different MPP configurations validate the model.