Abstract
本論文同時應用有限單元法及雙麥克風阻抗管實驗來探討多孔板/粗糙面吸音材之吸音特性。吸音材粗糙面包含三角型、凸半圓型、凹凸矩型與全平板型四種不同幾何形狀，而於上述不同幾何粗糙面前放置之多孔板亦有多種不同型式。結果發現，不同粗糙面形狀對較高頻率聲音的吸音係數影響較大，而若粗糙面吸音材前置有多孔板，則粗糙面形狀對吸音係數的影響不若粗糙面吸音材的多寡。另外，多孔板的開孔率、板厚、孔洞形狀與背後空氣層位置也會顯著的影響吸音係數。本論文最後亦以噪音衰減係數精簡評估結構的整體吸音能力，可供以後吸音結構設計之參考。The objective of this work is to study the influence of porousplates / acoustic absorbent materials with various shapes ofroughness surface on the sound absorption using finite elementmethod and two-microphone impedance tube experiment. Fourroughness surface shapes of acoustic absorbent materials, say,triangle, semi-circle, convex rectangle and plate shape, arechosen. Different porous plates are also placed in front of theabove acoustic absorbent materials to study the effect ofacoustic absorption in each assembly. It is found that thevariation of roughness surface shapes has more influence on theacoustic absorption coefficients at higher frequency. However,as the porous plates are placed in front of the acousticabsorbent materials, the influence of roughness surface shapeson the acoustic absorption coefficient is less than the amoumtof acoustic absorbent materials contained. The properties ofporous plates, such as porosity, thickness, shapes of holesand the location of back air gap, also affect the acousticabsorption coefficients distinctly. Finally, the noisereduction coefficient is adopted to simply indicate theacoustic absorbent ability of the entire structure, and wouldbe of help for the design of acoustic absorbent structure.