大部分吸音及隔音材料，為低密度和高孔隙率的材料，如岩棉、玻璃棉等。為了改善這些材料在中低頻之吸音效能表現，因而在原本多孔性材料上增加不同於原本孔隙特徵尺寸之孔洞大小，稱之為雙孔隙材料。由於兩種尺寸孔洞間之耦合效應亦稱為聲壓擴散現象，使雙孔隙材料能有效提升中低頻之吸音效能。但在隔音方面，若使用貫穿式開孔之雙孔隙材料，其隔音效能不佳。本研究探討雙孔隙材料的開孔率及開孔型式，如何影響雙孔隙材料吸音及隔音上的效能。本文使用Comsol有限元素分析軟體建立三維聲學數值模型，使用數種等效流體模型與Biot模型做為比較。其中Biot模型能同時描述固體與流體之聲學特性於數值分析中，較等效流體模型更便於同時應用在吸音及隔音分析。由分析模型與文獻實驗結果比對可知，能夠預測雙孔隙材料吸音效能的提升。透過雙孔隙材料之開孔率及開孔尺寸變化可調整吸音效能增加的頻率範圍。但是，當雙孔隙材料之開孔率增加時，隔音效能會降低，因隔音效能仍以單位面積之材料質量及流體阻力係數所主宰。

Most sound absorption materials are generally low density and high porosity, such as rockwool and glasswool. To improve the ability of sound absorption at low to medium frequencies, these porous materials are added meso-pores of size much bigger than the characteristic length of original micro-pores, as so-called double-porosity materials. Double-porosity materials can effectively improve the sound absorbing performance at specific frequency range, because of the coupling of meso-pores and micro-pores also referring to as pressure diffusion phenomenon. However, double-porosity materials behaves poorly in sound insulation. This research studied how the porosity and geometry of meso-pores improve the ability of double-porosity materials in sound absorption and insulation. Three-dimensional acoustic numerical models were developed using the finite element software Comsol. Several equivalent fluid models and Biot model were used as comparison. Biot model describes the acoustic vibration of solid skeleton and pore fluid, so it is more convenient to use in both sound absorption and insulation analyses than equivalent fluid models. From the comparison of numerical results and experimental data in the literature, the improvement in sound absorption for double-porosity materials can be predicted. Using different porosity and characteristic length of meso-pores, the effective frequency range can be adjusted. However, as the meso-porosity increases, the sound insulation performance will be reduced. Because the sound insulation is dominated by mass and flow resistivity per unit area.

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