Jute Felt for Noise Reduction: Understanding Effect of Pore Size Distribution

ABSTRACT

Effect of pore size and its distribution on the noise reduction coefficient of jute felt were studied through capillary flow porometer and impedance tube. The inter-criteria correlation method was used to optimize the type of jute felts to obtain noise reduction coefficient of 0.5. The porometry study of the needle punched jute felt suggested the gradient pore structure of felt due to presence of needling induced inverted cone of pores within fibrous mass. The jute felt with an areal density 796.5 g/m² with mean pore diameter 60.32 µm offered optimum noise reduction coefficient of 0.5. The percentage weight of pore distribution in the range of 45≥ ∅ <25 µm was 44.61%, indicated that to achieve an objective of NRC≥ 0.5 the most influential pore diameter range was 45≥ ∅ $<$25.The increased number of jute fiber per unit area of felts from 55 to 430 resulted in narrowing of inter fiber spaces and consequently reduced the mean pore size. Further increase in number of fibers ultimately leads to blocking of spaces within fibers and get compacted like a solid fibrous mass.

摘要

采用毛细管流变仪和阻抗管研究了孔径及其分布对黄麻毡降噪系数的影响. 采用准则间相关法对黄麻毡的类型进行了优化，得到了0.5的降噪系数. 针刺黄麻毛毡的孔隙率研究表明，毛毡的孔隙率呈梯度分布，这是由于针刺引起毛毡纤维团内出现倒锥状孔隙所致. 黄麻毡，面密度796.5g/m2，平均孔径60.32μm提供了0.5的最佳降噪系数. 孔隙分布的百分含量在45≥ ∅ <25μm为44.61%，表明要实现NRC的目标≥ 0.5影响最大的孔径范围为45≥ ∅ <25. 单位面积毛毡中黄麻纤维的数量从55根增加到430根，导致纤维间隙变窄，平均孔径减小. 纤维数量的进一步增加最终导致纤维内部空间的阻塞，并像固体纤维团一样被压缩.

关键词方法:

• 阻抗管
• 黄麻毡
• 降噪系数
• 孔径 声音
• KEYWORDS
• CRITIC method
• impedance tube
• jute felt
• noise reduction coefficient
• pore size
• sound

Additional information

Funding

This work was supported by the ICAR-National Agricultural Science Fund, New Delhi, India [NASF/ME/5016/2015-16].