| 摘要: | 伴隨著科技發展與工業技術快速發展及對生活品質的要求，噪音問題日益嚴重，因此降噪技術更為重要。目前市面上的吸音材料多屬於多孔介質材料，孔隙非常細小在內部可以均勻分布，因此纖維與纖維間存在著許多相互連通的孔隙；當聲波入射到材料表面時，一部分穿透進入材料內部，並且在微孔中左右傳遞，由於內部摩擦會消耗掉部分聲能，因而可以消耗聲波能量，達到吸音效果。
本研究選用兩種不織布結構，因為不織布本身結構具有較多的微孔，容易達到流阻效果，使聲波在材料內部產生摩擦，可使聲波能量減弱，達到吸收聲音的效果。研究方式是以疊層及複合兩種方式將熱壓不織布及熱烘不織布製成吸音材料，設計出不同的表面紋路及增加樣品的厚度及微孔對吸音效果進行測試，作為主要探討項目。
本研究設計以每單位面積出現 16 個 1 mm * 2 mm的方塊圖案作為基本的壓紋，利用超音波壓紋機以線條間距5 mm、10 mm，將熱壓不織布與熱烘不織布組合設計疊合型及複合型兩種組合，其圖案可在聲波傳遞到樣品表面，碰撞到壓紋高低差時使聲波干擾而達到吸收聲音的效果，此研究是以單層壓紋深度 0.2 mm，雙層壓紋深度 0.6 mm為模組。
從吸音性能實驗結果發現，不織布在低頻效果較好。在低頻聲能，可使聲波容易穿透樣品或吸收聲能的效果；在低頻率的吸音效果會隨頻率的增加而提高，到高頻範圍較不明顯。隨材料厚度加大，低頻吸音率呈現上升現象，高頻吸收率則呈現不明顯，而從各頻率的吸音效果發現三層熱烘不織布有明顯上升的趨勢。但當材料流阻越大，吸音係數也相對比較大，而過大的流阻則可影響吸音系統。研究結果顯示隨熱烘不織布厚度增加，內部的微孔也跟著變多，使得流阻率下降吸音率呈現下降現象。
在表面紋路吸音效果疊合型不織布，在高頻率部分組合 1 表面紋路距離為 10 mm較容易使聲波受到反射，使聲波相互碰撞產生共振效應而使聲音抵銷；就整體結果顯示聲音頻率越高，波長越短，聲能越小，能量波碰撞到不平滑表面或在微孔產生碰撞及反射，能量較容易被抵銷。表面紋路及厚度吸音效果疊合型組合 1，在中低頻率吸音效果最好，平均吸音率 0.72 ，厚度增加吸音效果也跟著增加，增加了 15 mm (3 層) 厚度的熱烘不織布，吸音效果在低頻區域的平均吸音率達 0.72 ，在高頻率吸音效果較好，吸音曲線較趨近，可得知高頻率的聲波在壓紋深度較深及整體厚度增加可以達到吸收聲音的效果，所以在疊合型不織布組合，因為整體厚度與流阻產生變化，因此在高頻率的吸音效果越佳。
複合型不織布表面紋路吸音效果，組合 3 表面紋路距離為 10 mm 在中低頻部分吸音率的曲線明顯的上升，特別在頻率 1000 Hz吸音率達到 0.98 ，組合 3 紋路距離 10 mm較有利於低頻率音波入射；組合 4 表面紋路距離為 5 mm ，在中高頻率部分吸音率有上升的趨勢，且在頻率 4000 Hz吸音率達到 0.73 ，組合 4 的吸音曲線漸漸上升，可得到組合4紋路距離有利用於在高頻率吸收聲能。組合 4 增加了 15 mm ( 3層 )厚度的熱烘不織布，吸音效果在低頻區域的平均吸音率達 0.5 ，可得知高頻率的聲波在壓紋深度較深及整體厚度增加可以達到吸收聲音的效果，平均吸音率在 0.45 。表面紋路及厚度吸音效果複合型組合 3 在高頻率 2000 - 4000 Hz 吸音效果則是有上升的趨勢，平均吸音率達 0.51 ；複合型組合 4 在頻率 500 Hz中，吸音效果最好達到 0.89 ，中高頻率的部分吸音率有上升的趨勢，平均吸音率達到 0.73 ，由此證明增加厚度可使吸音效果也跟著些微增加。
With the rapid development of technology and industrial technology and the demand for quality of life, noise problems are becoming more and more serious, so noise reduction technology is more important. At present, the sound absorbing materials on the market mostly belong to porous media materials. There are many interconnected pores between the fibers and the fibers. The pores are very fine and evenly distributed inside. When the sound waves are incident on the surface of the material, a part penetrates into the interior of the material. The holes are transmitted to the left and right, and some of the sound energy is consumed by the internal friction to achieve the consumption of sound waves.
In this experiment, two kinds of non-woven fabric structures are selected, because the non-woven fabric itself has more micropores, which is easy to generate flow resistance, so that the sound waves generate friction inside the material, which can weaken the sound energy and achieve the effect of absorbing sound. The hot-pressed non-woven fabric and the hot-baked non-woven fabric are made into a sound absorbing material in a laminated and composite manner, and different surface textures are designed, the thickness of the sample is increased, and the sound absorption effect of the micropores can be tested as a main discussion item.
In this study, This study was designed to occur 16 unit in the one square 1cm2 ,a unit of W*L 1 mm * 2 mm square pattern embossed as a basic . The ultrasonic embossing machine is used to combine the hot-pressed non-woven fabric and the hot-drying non-woven fabric with a line spacing of 5/10mm. Two types of combinations, the pattern can make the sound wave interfere with the embossing height difference when the sound wave is transmitted to the surface of the sample to achieve the sound absorption effect. The single-layered grain depth is 0.2mm, and the double-layered grain depth is 0.6mm.
Firstly, from the results of sound absorption performance experiments, it is found that non-woven fabric has better effect at low frequency. At low frequency sound energy, sound waves can easily penetrate the sample or absorb sound energy. The sound absorption effect at low frequency will increase with the increase of frequency to high. The frequency range is not obvious. As the thickness of the material increases, only the low-frequency sound absorption rate rises, and the high-frequency absorption is not obvious. From the sound-absorbing effect of each frequency, it is found that the three-layer heat-drying non-woven fabric has a significant upward trend. However, when the material flow resistance is larger, the sound absorption coefficient is relatively large, and the excessive flow resistance will affect the normal operation of the ventilation system. Then, as the thickness of the heat-drying nonwoven fabric increases, the internal micropores become more and more, resulting in a decrease in flow resistance. Surface texture sound absorbing effect superimposed type non-woven fabric, in the high frequency part combination 1 surface grain distance is 10 mm, it is easy to make the sound wave reflected so that the sound waves collide with each other to produce a resonance effect to offset the sound; the overall result shows that the higher the sound frequency, the higher the wavelength Short, the smaller the acoustic energy, the energy waves collide with the unsmooth surface or collide and reflect in the micropores, and the energy is easily offset. The combination of surface texture and thickness sound absorption effect is the best in the middle and low frequency, the average sound absorption rate is 0.72, and the thickness is increased. The sound absorption effect is also increased. The heat-drying non-woven fabric with a thickness of 15mm (3 layers) is added. The average sound absorption rate in the low frequency region is 0.72. The sound absorption effect at high frequency is better, and the sound absorption curve is closer. It can be known that the high frequency sound wave can achieve the effect of absorbing sound when the embossing depth is deep and the overall thickness is increased. The combination of non-woven fabrics, because the overall thickness and flow resistance change, so the sound absorption at high frequencies is better.
The composite surface of the non-woven fabric has a sound absorption effect. The combination of the surface roughness of the surface is 10 mm. The curve of the sound absorption rate in the middle and low frequency is obviously increased, especially at a frequency of 1000 Hz, the sound absorption rate is 0.98, and the combined 3 grain distance is 10 mm. Incident; the surface distance of the combination 4 is 5 mm, the sound absorption rate increases at the middle and high frequency, and the sound absorption rate reaches 0.73 at the frequency of 4000 Hz. The sound absorption of the combination 4 is gradually increased, and the combined 4 grain distance is advantageously used. Absorbs acoustic energy at high frequencies. Combination 4 adds 15mm (3 layers) thickness of hot-baked non-woven fabric, and the average sound absorption rate of the sound-absorbing effect in the low-frequency region is 0.5. It can be known that the high-frequency sound wave can achieve the effect of absorbing sound when the embossing depth is deep and the overall thickness is increased. The average sound absorption rate is 0.45. Surface texture and thickness sound absorption effect composite combination 3 has a rising trend in high frequency 2000-4000 Hz sound absorption, the average sound absorption rate is 0.51; composite type 4 in frequency 500 Hz, the sound absorption effect is best to reach 0.89, medium high Part of the frequency has a rising rate of sound absorption, and the average sound absorption rate reaches 0.73, which proves that increasing the thickness can increase the sound absorption effect. |
