Measurement of perforate impedance with grazing flow on both sides

Abstract

© 2016 by M. Farooqui, T. Elnady and M. Åbom. In this paper, the acoustic impedance of a microperforated plate (MPP) with two-sided grazing flow is educed by a modified semi-analytical inverse technique. The MPP sample is placed in the middle of a rectangular duct with grazing flow. The mode matching formulation is derived in terms of pressure for a MPP with two-sided grazing flow. The inputs to this mode matching technique are complex acoustic pressure measured at twelve positions at the wall of the duct, upstream and downstream of the MPP section. First the ability of the code to reproduce the pressure field for a given impedance is tested. Second the ability to educe the correct impedance for a given pressure distribution is tested. The results of the mode matching code are in good agreement with the simulations for no flow cases.