<![CDATA[ Conventional building materials are energy-intensive and generate substantial waste, motivating the valorization of agricultural by products into sustainable acoustic materials. This study developed an acoustic panel from Coconut Fiber (CF) and Spent Coffee Grounds (SCG) bound with a cassava starch-based adhesive, with SCG incorporated at 0%, 15%, and 30% (samples A1, A2, and A3, respectively). SCG addition increased panel density from 208.9 kg/m3 (A1) to 247.5 and 268.7 kg/m3 for A2 and A3. Tensile testing showed that SCG reduced the maximum stress while increasing the Young's modulus, indicating a trade-off between ductility and stiffness. Scanning electron microscopy revealed that SCG particles bridged the coconut fiber network, altering the pore structure and air-flow resistivity. Sound absorption coefficients measured across 250-5000 Hz using the impedance tube method showed that A2 (85% CF, 15% SCG) achieved the best overall performance, reaching coefficients of 0.86 at 500 Hz and 0.69 at 250 Hz and outperforming A1 and A3, particularly at low-to-mid frequencies. Excessive SCG in A3 reduced absorption due to increased density and reduced porosity. These findings demonstrate that CF-SCG composite panels are a promising, low-cost, biobased alternative to conventional acoustic materials and SCG for balancing sound absorption performance with sustainable resource valorization.]]>
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