Sound Absorption Coefficient Analysis for Composite Made of Agricultural Waste

The background of this study is to reduce and reuse agricultural waste, specifically rice husk and rice straw waste. This research aimed to determine the sound absorption coefficient / noise absorption coefficient (NAC) of a composite material made of rice husk and rice straw so that it can be used as an alternative acoustic material. Rice husk and straw were processed into composite materials using a polyester matrix with a volume fraction of 30:70 and sample thickness variations of 25 mm and 40 mm. In addition to treating variations in sample thickness, samples were made with different cavity holes diameter variations, including flat (without cavity holes), 3 mm, and 4 mm with 10 mm cavity depth. Samples were tested using a type 4206 impedance tube with two microphones according to the ASTM E1050 standard in the 200 – 1600 Hz frequency range. According to the findings of this study, the maximum sound absorption coefficient value of the rice straw composite material is obtained from samples with a thickness variation of 40 mm and a cavity diameter of 3 mm, with α value of 0.87 at a high frequency of 1,600 Hz. Meanwhile, the rice husk composite material's maximum sound absorption coefficient value was obtained from samples with a thickness variation of 40 mm and a cavity diameter of 3 mm with α value of 0.65 at a low frequency of 400 Hz. According to the findings of this study, rice straw composite material and rice husk composite material have different properties as sound absorbing materials and can be used as acoustic materials in a specific frequency range.