Improving the Sound Absorption of Natural Waste Material-based Sound Absorbers Using Micro-perforated Plates

ABSTRACT

Both natural and synthetic fibers do not perform well at low frequencies and are also subjected to erosion, moisture, fire, etc., when used as an interior finish of room walls. To overcome these problems, micro-perforated plate with different thickness is used in a multilayer sound absorber configuration to improve its sound absorption. Firstly, the acoustic properties of five natural wastes including sheep wool, goat wool, camel wool as well as pith and fiber bundles of sugarcane bagasse were determined by using an impedance tube following ISO 10534–2. Secondly, the effect of Panel thickness was investigated. The maximum sound absorption coefficient (SAC) of natural waste materials is at middle to high-frequency range and this shifted to lower frequency as the porous layer thickness increases. The sound absorption performance depends on the thickness of perforated plate and porous layer in a compound sound absorber. It is observed that the using perforated plate in the front of low thickness porous materials significantly improve the SAC and absorption bandwidth. However, it should be noted that this reduces the SAC at high frequencies. Accordingly, the thick micro-perforated panels backed by porous layer are not recommended to control sounds with frequency higher than 3000 Hz.

摘要

天然纤维和合成纤维在低频率下的性能都不好，当用作房间墙壁的内部饰面时，也会受到侵蚀、潮湿、火灾等的影响. 为了克服这些问题，在多层吸声结构中采用不同厚度的微穿孔板来提高吸声性能. 首先，采用符合ISO10534-2标准的阻抗管，对羊毛、山羊毛、骆驼毛、甘蔗渣的髓和纤维束等5种天然废弃物的声学特性进行了测试. 其次，研究了壁板厚度的影响. 天然废弃物的最大吸声系数（SAC）处于中高频范围，随着多孔层厚度的增加，最大吸声系数向低频方向移动. 复合吸声器的吸声性能取决于穿孔板和多孔层的厚度. 结果表明，在低厚度多孔材料的前端使用多孔板可以显著地提高SAC和吸收带宽. 然而，应该注意的是，这减少了高频下的SAC. 因此，不建议使用多孔层支撑的厚微孔板来控制频率高于3000 Hz的声音.

KEYWORDS:

• Sound
• micro-perforated plate
• natural waste
• fiber
• sugarcane
• wool

关键词:

• 声音
• 微孔板
• 天然废弃物
• 纤维
• 甘蔗
• 羊毛

Acknowledgments

This study is part of a Ph.D. dissertation (ethics code no. IR.MODARES.REC.1398.115) which is registered in the Research Department of Medical Sciences of Tarbiat Modares University, Tehran, Iran, and supported by the National Institute for Medical Research Development (NIMAD, Elite Researcher Grant proposal No.987822]of Iran. The authors would like to thank Deputy of Research and Technology, Tarbiat Modares University and NIMAD for providing the required laboratory facilities for conducting this work.

Additional information

Funding

This work was supported by the National Institute for Medical Research Development (NIMAD, Elite Researcher Grant proposal No.987822]of Iran ;Tarbiat Modares University of Iran [ethics code no. IR.MODARES.REC.1398.115];