Acoustical behaviour of natural fibres-based composite boards as sound-absorbing materials

摘要

The studies on acoustical behaviour of composite boards made from five different types of natural fibres (bagasse, bamboo, banana, coir and corn husk) have been carried out for their utilization as sound-absorbing materials. The composite boards of all five types of fibres were prepared in three different density range (low, medium and high). The ranges of low, medium and high density boards varied from 280 to 300 kg/m(3), 320 to 350 kg/m(3) and 400 to 450 kg/m(3), respectively. The porosity, which was calculated based on bulk board density and fibre density, was found to vary from 50 to 79% depending upon the types of fibres and density of board. The damping coefficient (tan delta) was determined using dynamic mechanical analyzer and found maximum (0.09) in banana and corn husk fibre boards having density 280-297 kg/m(3)). The variation of sound absorption coefficient of fibre boards with frequency (up to 4 kHz) was measured. The noise reduction coefficient (NRC), which was calculated as an average of sound absorption coefficient values at 250, 500, 1000 and 2000 Hz, was found to decrease with the increase in board densities for all the five types of boards. The maximum NRC value of 0.40 was found for banana fibre boards having density of 280 kg/m(3) and therefore found comparatively more suitable as sound absorbing material.