Acoustic Evaluation of Starch Polymer Composites Reinforced with Reed and Coconut Fibers

This research developed an environmentally friendly sound-insulating material from a starch biopolymer matrix, reinforced with common reed (Phragmites australis) and coconut (Cocos nucifera) fibers at weight fractions of 10%, 20%, and 30%. Physicochemical, thermal, and mechanical characterization through FTIR, TGA, and Shore O hardness test confirmed the formation of a thermally stable, amorphous biopolymer composite. Morphological analysis revealed average fiber diameters of 0.38 mm for reed fibers and 0.26 mm for coconut fibers, creating a structural difference that directly influences performance. The results indicated that reed fibers provide greater mechanical rigidity and compaction, while the finer coconut fibers promote a highly porous architecture ideal for sound dissipation. Acoustic evaluation using an impedance tube yielded absorption coefficients of 0.7–0.9 at high frequencies, matching the performance of commercial polyurethane foam and fiberglass. These findings demonstrate a functional synergy in which coconut fibers enhance acoustic absorption, while reed fibers ensure structural stability. The developed materials represent a renewable and biodegradable alternative for application in construction and interior design. Future research should further evaluate behavior under humidity and long-term mechanical resistance to optimize overall performance