吸音材料受壓縮後之性能探討

Abstract

本文探討吸音材料在受到壓縮作用後其吸音能力的改變情形，利用Biot彈性多孔材理論與彈性固體理論分別推導出在空氣中與水中其材料之波動方程，探討當材料受壓縮作用後其各參數之變化情形，考慮材料兩端速度與應力的連續條件，可建立聲波之轉換矩陣，進而求得材料吸音率與回聲衰減量。本文分別就空氣中與水中兩部份探討材料之吸音效能的變化情形。 空氣中的部份探討了多孔材受壓與否之吸音效能比較，亦嘗試以不同角度入射時其吸音能力的變化情形；而當吸音材料受壓縮作用後，整體之吸音曲線會往高頻處平移，其吸音效能比不受壓時略為降低。但若比較相同厚度的多孔材，材料受到壓縮作用會比材料無受壓之情形其吸音效果要佳。水下的部份則模擬材料承受水壓後，吸音效能因材料厚度、聲能損耗性質改變所造成的影響，導致於整體之吸音效能變差。

This work studies that the sound is muffled by the acoustic material which is compressed. For yielding the sound wave equation of the material in water or air, Biot theory and the sound propagation of the solid are used. Furthermore, the variation in the acoustic parameters is presented and discussed. By considering the boundary conditions, the continuous velocity and pressure on the both sides of the material, the sound transfer matrix can be build. Than the absorption coefficient and the echo reduction can be calculated. The two parts, the sound absorptions of the material in air and water are researched separately. In the one part, the abilities of sound absorption of the compressed material in air are investigated. The influence of the different incident angles of sound wave are also discussed in the article. As the acoustical material is compressed, the characteristics (peak or tip) of curve of absorption coefficient shift to high frequency. The value of absorption coefficient becomes low. On the other side, as the both thicknesses of the compressed and the un-compressed porous materials are the same, the ability of absorption of compressed material is better than another un-compressed material. In the other part, the work focuses on the acoustic studies in water. As the thickness of the material varies from the pressure of water, the influences on the abilities of sound absorption of the material are simulated. In water, the ability of absorption of material is bad because the pressure of water lead the property of the material to change.