Acoustic properties of perforated plates and screens
Résumé
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-ChampouxAllard for the micrometric mesh was developed. This model is in very good agreement with experimental results.
Domaines
Acoustique [physics.class-ph]Origine | Fichiers éditeurs autorisés sur une archive ouverte |
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