Assessment of natural-fiber ceiling materials for room acoustics: COMSOL Multiphysics simulation

Abstract

Low-frequency indoor noise is difficult to control in small rooms because standing waves create strong spatial non-uniformity and resonance-driven peaks in sound pressure level (SPL). This study assessed sustainable porous ceiling treatments made from coconut fibre and sugarcane fibre using three-dimensional frequency-domain simulations in COMSOL Multiphysics (Pressure Acoustics). A 9 m × 3 m × 3 m furnished room was modelled with rigid walls and floor, while the ceiling was varied between a fully reflective default case and porous ceiling layers of 100, 200, 300, 400, and 500 mm for coconut fibre and sugarcane fibre porous. The porous ceilings were modelled using the Johnson–Champoux–Allard model, with material parameters taken from peer-reviewed sources and absorption coefficient data derived from impedance tube measurements of coconut fibre and sugarcane fibre composite specimens. Sound pressure level (SPL) was measured at receiver distances of 4.5 m and 9 m for standard 1/3-octave centre frequencies from 125 to 2000 Hz under source levels of 50, 70, and 90 dB. Both natural-fibre ceilings produced the largest SPL reductions in the mid and high bands, primarily by suppressing modal peaks around 1000–1250 Hz, while improvements at 125–250 Hz were smaller and more position dependent. Most of the frequency-averaged reduction was achieved at 20 cm thickness, with a smaller increase for thicker layers. The results support natural-fibre porous ceilings as practical, low-impact options for improving room acoustic conditions in the wave-dominated region and may be used as sustainable ceiling treatments for enhanced indoor acoustic comfort.