Keywords: perforated plate, multiple hole sizes, porous separating partition, wide-band frequency absorption, optimization, finite element, effective density.

In this paper, a new type of wide-band frequency absorption characteristic realization of a perforated plate is proposed. Unlike existing research, our perforated plate model consists of multiple hole sizes and a porous separating partition. For wide-band frequency absorption performance, some parameters such as multi-layered perforated plates, internal porous layers and a different cavity depth by separating the partition were investigated by previous researchers. In this paper, finite element simulation is used for the analysis and optimization of our perforated plate model. Finite element analysis can be good alternative to the theoretical approach when complex calculations for the surface impedance of the perforated plate is difficult. To model the absorption mechanism occurring in the plate hole, the effective density appropriate for the finite element simulation is calculated from the rigid frame porous model (the Johnson-Champoux-Allard model), which is equivalent to an existing surface impedance model (the Beranek-Ingard model). As the radiation phenomenon around the hole is implemented directly in the acoustic finite element simulation, only the viscous effect at the hole surface needs to be considered additionally in the finite element simulation. Also for the material properties of porous separating partition, the Delany-Bazley model was used. After some verification using simple examples, the wide-band frequency absorption analysis was conducted with variations of some parameters. Then the parameters of perforated plate were optimized using a size optimization method.

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