SUSTAINABLE ACOUSTIC ENCLOSURE USING RUBBERWOOD PROCESSING BY-PRODUCTS AND NATURAL RUBBER LATEX

Noise generated by industrial machinery, particularly air compressors, requires effective and sustainable control measures. This study developed and evaluated a detachable acoustic enclosure incorporating eco-friendly sound-absorbing panels fabricated from rubberwood processing by-products-sawdust and biomass bottom ash-bonded with natural rubber latex (NRL) as a bio-based binder. The optimal compositions for achieving dimensional stability, adhesion, and moldability were identified through panel fabrication experiments as sawdust–NRL composite (1:1.5) and sawdust/ash-NRL composite (0.5:0.5:1). Physical characterization showed that sawdust/ash composite panels exhibited higher bulk density due to ash-induced matrix densification. The acoustic performance of the developed materials was assessed over the 125-4,000 Hz frequency range using wooden enclosures lined with various absorptive materials, with results revealing clear frequency-dependent noise attenuation. At low frequencies (125-250 Hz), the wooden enclosure without lining provided the greatest attenuation due to resonant panel absorption. In the mid-frequency range (250-2,000 Hz), sawdust and sawdust/ash composite panels exhibited higher sound attenuation efficiency than conventional polyurethane and polystyrene foams, highlighting the role of porous biomass structures in acoustic energy dissipation. At high frequencies (2,000-4,000 Hz), the biomass-based panels outperformed the synthetic foams, with sawdust composites achieving noise reductions of up to 25 dBA, corresponding to ~95% reduction based on linear sound pressure levels. This study demonstrates the potential of biomass-based acoustic materials as practical and sustainable solutions for noise control in small-scale industrial environments, offering an effective alternative to conventional synthetic absorbers for improving occupational acoustic conditions.