Fabrication of Chemically Treated Natural Fibre Reinforced Polymer Matrix Composites and Measurement of its Sound Absorption Coefficients to Regulate Industrial Noise

The effects of chemically treated natural fibres (rice straw and kenaf) embedded as filler into polypropylene matrix were investigated for its sound absorption properties to regulate the industrial noise. In this respect, untreated natural fiber as well as treated natural fiber reinforced with polypropylene composites were fabricated and compared. The composites were prepared by compression moulding technique. Its sound absorbing characteristic was investigated with the Impedance tube, according to a transfer function method. A two microphone setup was fabricated according to American society for testing materials ASTM E1050-10 and it is used to measure sound absorption coefficients of composites in the frequency range of 300 Hz to 2000 Hz. The sound absorption coefficients of the composites increased with the frequency. However, at 1000 Hz, the sound absorption coefficient decreased for all treated samples and then increased again which is due to specific character of natural fibers. This point of inflexion was due to the specific characteristic of natural fiber reflecting sound at around 1000 Hz, but absorbing sound in the middle and high frequencies. The results indicates that the process of chemical treatment enhanced the sound absorption coefficients by 12.5% for rice straw reinforced Polypropylene and 15.78% for kenaf fiber reinforced Polypropylene composites respectively.