Temiz Muttalip Aşkın, Lopez Arteaga Ines, Efraimsson Gunilla, Åbom Mats, Hirschberg Avraham
Department of Mechanical Engineering, Dynamics and Control, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Department of Aeronautical and Vehicle Engineering, Centre for ECO2 Vehicle Design, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
J Acoust Soc Am. 2015 Dec;138(6):3668-77. doi: 10.1121/1.4937748.
Global expressions are proposed for end-correction coefficients in micro perforated plates (MPPs) using non-dimensional parameters. MPPs are sound absorbers with small perforation diameters such that the Stokes boundary layers fill up almost the entire perforation. Sound absorption does not only occur within the perforation, but also takes place just outside of it. The latter contribution plus the outside inertia effect on the transfer impedance of the MPP are referred to as end-corrections. In order to determine them, an analytical solution employing the very thin Stokes layer assumption has been derived. However, this assumption requires empirical coefficients in the end-corrections for accurate results. To explore the effects of various parameters a numerical model is used. This model is verified with open-end reflection coefficient measurements. The most prominent result from this study is that compared to plate thickness, the ratio of perforation diameter to Stokes layer thickness (Shear number) and edge geometry affect the end-correction coefficients more significantly. The effect of plate thickness can be neglected for practical purposes, therefore, expressions for the end-corrections in terms of Shear number and edge geometry are provided. The relative error of these expressions is <3% compared to the numerical results.
