Evaluating Coir Composites As Eco-Friendly Sound Absorbers: An Experimental And Comparative Approach

Abstract

With growing global emphasis on sustainable construction and effective noise control, this study explores the acoustic performance of coir-based composites as environmentally friendly alternatives to synthetic sound absorbers. Four material types—Coir Matting, Coir Needle Felt, Low-Density Coir Composite Board (LDCCB), and Medium-Density Coir Composite Board—were fabricated and evaluated using the ASTM E1050–12 impedance tube method. Among these, LDCCB achieved the highest average Sound Absorption Coefficient (SAC) of 0.65 in the 500–2000 Hz range, attributed to its low density (300–400 kg/m³), high porosity, and interconnected fiber structure. This performance surpasses traditional coir matting (SAC: 0.56) and compares favorably with untreated coconut fiber. The study also includes comparative analysis with other natural fibers such as kenaf, PALF, and sugarcane bagasse. While kenaf displayed a higher peak SAC (0.90 at 2000 Hz), its greater density and lower durability underscore LDCCB’s advantages in sustainable applications. Hybrid coir-jute composites extended absorption into higher frequencies (SAC: 0.72 at 5000–6300 Hz), and simulation results showed that reducing coir fiber diameter can significantly enhance low-frequency performance. Furthermore, LDCCBs demonstrated excellent thermal insulation (0.098 W/m·K) and maintained acoustic efficiency without compromising mechanical stability at lower densities. These findings validate LDCCBs as multifunctional, regionally available, and low-carbon acoustic materials suitable for diverse green building applications such as panels, tiles, and insulation systems, reinforcing their potential for commercial use in sustainable architecture.