本文利用ABAQUS有限元素數值分析建立多孔性材料之二維聲學模型，模型包含固體及流體(空氣)兩種介質，變化介質幾何與排列組合，以探討微觀結構對多孔材料的聲學表現之影響，並將部分結果與聲學理論分析比對。特徵阻抗的實部與虛部，分別代表介質具有儲能能力與消能能力，其中消能能力又稱為吸音能力。本文數值分析中，開孔型結構在聲波傳遞方向上可以經由固體與流體兩種介質平行並進，而閉孔型結構在聲波傳遞方向上需經過固體/流體介質先後交錯。因此結果顯示，開孔型結構較能發揮孔洞摩擦所產生之聲能損耗，而閉孔形結構則容易產生固體層共振頻。為了達到理想的吸音能力，預計應以開孔型結構為表面層。如果想要在分析頻率範圍內有平均的隔音能力，開孔型結構所產生之聲能損耗似乎居於主導因素。但隔音性能的提升，仍然是以高面密度的固體為主。

SUMMARY

In this paper, finite element method is used to analyze the acoustic properties of porous materials. Two-dimensional acoustic models were built in ABAQUS. In the models, the porous materials contain two medium, which are solid skeleton and fluid (air) in the pores. By arranging the pore structures in the models, we explore its influence on the acoustic performance of porous material. In the open-cell model, the solid and fluid are arranged in parallel to the direction of sound propagation. In the closed-cell model, the solid were arranged in series with the fluid in along the direction of sound propagation. The results show that open-cell structure dissipates sound energy by the volumetric drag of pore fluid. In order to improve sound absorption ability, we shall expect the use of open-cell material in the surface layer. Meanwhile, open-cell structure also provides good sound insulation in a wide frequency range due to volumetric drag. Closed-cell structure often show strong resonance in the analyses, which indicates the effects of pore structure. Our analyses can be extended further to explore more on the effects of pore structures and the connectivity of pores.

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