Acoustic properties of perforated plates and screensReport as inadecuate

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* Corresponding author 1 DRIVE - Département de Recherche en Ingéniérie des Véhicules pour l-Environnement

Abstract : In previous works, an acoustic model for Microperforated Insertion Unit MIU, was developed to determine the input impedance of a system composed of a thin mesh or screen glued onto a perforated plate. An alternative approach is proposed by means of the equivalent fluid model of Johnson-Champoux-Allard involving five physical parameters: the tortuosity, the thermal and viscous characteristic lengths, the porosity and the flow resistivity. The input impedance of a multiple layer system can then be found by use of the transfer matrix method. Since the meshes have fairly simple structures, it was possible to model an elementary representative cell and to use calculated values for the five parameters. The resistivity was also evaluated from absorption measurement for the screen alone in an impedance tube. For the thermal and viscous characteristic lengths, the calculated values were also compared to measurements obtained from a microscope image of the elementary cells of the screen. A hybrid model using the theory by Maa for the perforated plate and the theory by Johnson-Champoux–Allard for the micrometric mesh was developed. This model is in very good agreement with experimental results.

Author: Heidi Leni Ruiz Villamil Pedro Cobo Thomas Dupont - Philippe Leclaire -



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