Experimental and Theoretical Investigation of the Acoustic Absorbers Fabricated from Natural Kenaf Fibres and Rice Husk

ABSTRACT

Fabrication of acoustic absorbers from a combination of natural waste materials is a novel approach in the field of noise control. The aim of this study was to investigate the acoustic absorption performance of several sample sound absorbers made from natural kenaf fibers and rice husk. A new method of fabricating these sample sound absorbers was also employed to study the usability as well as performance improvement via the approach fibro-granular sound absorbers (FGSA). The values of acoustic absorption performance, porosity, and airflow resistivity of the samples were used in the experimental design. The Dunn and Davern (D-D) theoretical model as well as the reversed D-D model with Nelder–Mead Simplex were applied to evaluate the sound absorption as well. According to the obtained values, it was found that at low- and mid-frequency range, the sound absorption value of FGSA is higher than other acoustic materials. The FGSA (with a density of 150 kg/m³) increased noise reduction coefficient value by 31.25% compared to samples fabricated to the rice husk and also by 10.53% compared to kenaf. Based on comparison of the theoretical and experimental results, the model optimized with the Nelder–Mead method had higher accuracy and fitting in predicting the sound absorption values than the D-D model. Finally, it was found that improvement in the sound absorption performance of the natural acoustic absorbers might be achieved through adopting the approach of combining natural materials and fabrication of FGSA.

摘要

利用天然废弃物制造吸声材料是噪声控制领域的一种新方法. 本研究的目的是研究几种由天然红麻纤维和稻壳制成的样品吸声器的吸声性能. 此外, 还采用了一种新的制备样品吸声器的方法, 通过“纤维颗粒吸声器”(FGSA)的方法来研究其可用性和性能改进. 实验设计中使用了样品的吸声性能、孔隙率和气流电阻率(AFR)值. 采用Dunn和Davern(D-D)理论模型以及Nelder-Mead单纯形(NMS)反向D-D模型来评估吸声效果. 根据获得的数值, 发现在低频和中频范围内, FGSA的吸声值高于其他声学材料. FGSA(密度为150kg/m3) 的降噪系数(NRC)值比稻壳制成的样品提高了31.25%, 也比红麻提高了10.53%. 通过理论和实验结果的比较, 用Nelder-Mead方法优化的模型比D-D模型在预测吸声量方面具有更高的精度和拟合度. 最后发现, 通过采用天然材料与FGSA制备相结合的方法,可以提高天然吸声材料的吸声性能.

KEYWORDS:

• Natural materials
• sound absorption
• fibro-granular
• empirical model

关键词:

• 天然材料
• 吸声
• 纤维颗粒
• 经验模型

Acknowledgment

We are thankful to the Mazandaran University of Medical Science for providing the necessary laboratory facilities for this work.

Disclosure statement

The author(s) declare that there is no conflict of interests regarding the publication of this paper.

Additional information

Funding

This work was supported by Mazandaran University of Medical Science, Sari, Iran [Grant No: 8826, IR.MAZUMS.REC.1400.8826].