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This paper highlights the sound absorption performance of microperforated panel (MPP) made from coconut fiber and polylactic acid (PLA) composite named as biocomposite microperforated panel (BMPP). Coconut fiber was used to produce BMPP specimen and PLA was used as matrix. Impedance tube method was employed to identify the sound absorption performance of BMPP specimen while a porosity tester was used to determine the porosity of BMPP specimen. Comparison on the sound absorption performance between BMPP and steel MPP will be discussed in this paper. It has been found that BMPP with different composition percentage of coconut fiber and PLA possessed different sound absorption performance mainly due to the existence of pores and tortuous structure within the specimen itself. Scanning electron microscope (SEM) scan was performed to further analyze the structure of BMPP specimen. [ABSTRACT FROM AUTHOR]

Oil palm mesocarp fibre is seen as one potential of reinforcement in polymers due to its high strength, low cost, environmentally friendly nature and availability. Recently, it has attracted greater interest from academia and industries due to its potential for making a low-cost sound absorption panel. Therefore, this study is obliged to investigate the acoustic characteristics and the physical properties of oil palm mesocarp fibre (OPMF) as a porous material for sound absorbing panel. The measurements of the sound absorption coefficient are determined by using: (1) analytical model of Delany-Bazley, (2) analytical model of Johnson-Champoux-Allard, and (3) experiment of the impedance tube method. A commercial polyurethane (PU) was used as a composite binder during the intermixing process with the fibres. The manufacturing parameters are 10/90, 20/80, 30/70 and 40/60 by wt.% of PU/OPMF. The outcome shows that adding binder compacts the fibre by reducing the pore diameter and porosity, thus increasing the flow resistivity. Results also indicate that Johnson-Champoux-Allard model can justify the overall trend of absorption of the coefficient perfectly in contrast to the Delany-Bazley model. Overall, OPMF with 10 wt.% PU binder displayed greater absorption from low to mid-frequency range and the highest value of noise reduction coefficient of 0.66, while fibres with 20 wt.% PU produced the highest value of sound absorption coefficient of 0.99 at 1000 Hz. The results conclude that oil palm mesocarp displays a potential and brighter prospect to be implemented as a sound absorption panel as demonstrated in this study. [ABSTRACT FROM AUTHOR]

Natural fibres are significantly used as reinforcements in manufacturing low-cost and lightweight polymer composites; other advantages include being innoxious to human, easily obtained, and having a higher capacity of biodegradability. Therefore, researchers divert their attentions to finding sustainable and eco-friendly materials such as natural fibres to be an alternative sound absorber. This paper discusses the use of natural fibre from the Kenaf fibre (Hibiscus Cannabinus), which qualifies as an acoustical material to control undesired noise. This selected natural fibre is famous in South East Asia countries and has a wide plantation. Sound absorption properties of this natural fibre have been investigated. During the processing stage, Kenaf fibres are treated with alkaline treatment; 2% individually and boundwith various percentages of natural rubber (latex). The thickness of each sample is kept constant at 50mm only. Their acoustic performance was evaluated by using an impedance tube instrument. The result shows that Kenaf reaches the maximum absorption coefficient value towards low frequency when the fibre samples are bound with natural rubber. Fibres without the binder reach a high-frequency range of 4000 Hz and above. The physical characteristics of Kenaffibres such as density, porosity, and flow resistivity were also tested. The results demonstrate that this selected natural fibre is a promising light and environmental-friendly sound absorption material. [ABSTRACT FROM AUTHOR]

Introduction. Prolonged exposure to hand-transmitted vibration from grass-cutting machines has been associated with increasing occurrences of symptoms and signs of occupational diseases related to hand-arm vibration syndrome (HAVS). Methods. A cross-sectional study was carried out using an adopted HAVS questionnaire on hand-arm vibration exposure and symptoms distributed to 168 male workers from the grass and turf maintenance industry who use hand-held grass-cutting machines as part of their work. The prevalence ratio and symptom correlation to HAVS between high and low-moderate exposure risk groups were evaluated. Results. There were positive HAVS symptoms relationships between the low-moderate exposure group and the high exposure group among hand-held grass-cutting workers. The prevalence ratio was considered high because there were indicators that fingers turned white and felt numb, 3.63, 95% CI [1.41, 9.39] and 4.24, 95% CI [2.18, 8.27], respectively. Less than 14.3% of workers stated that they were aware of the occupational hand-arm vibration, and it seemed to be related to the finger blanching and numbness. Conclusion. The results suggest that HAVS is under-diagnosed in Malaysia, especially in the agricultural sectors. More information related to safety and health awareness programmes for HAVS exposure is required among hand-held grass-cutting workers. [ABSTRACT FROM AUTHOR]