Acoustic absorption phenomena of fibro-granular composites

The current study was conducted to enhance the acoustic absorption performance of fibrous materials. The industrially prepared fiber has thinner diameter compared to the fresh fiber. This reduction in the diameter of industrial fibers is observed due to various chemical treatments, at the cost of the removal of moisture contents. In previous studies the acoustic absorption performance of single fibrous material showed lower acoustic absorption at low frequency region. Current research is initiated to improve this shortcoming by combining the granular materials with fibrous materials. This new composite of fiber and grain is named as fibro-granular composite. The acoustic absorption performance of this composite which is the combination of coir fiber and rice husk, is illuminated in this paper in terms of the simple Delany-Bazley and rigid frame Johnson-Champoux-Allard model. The calculated value of the sound absorption coefficient of coir fiber-rice husk composite is compared to the simple coir fiber composite in order to validate the analytical results. The comparison shows the better acoustic absorption performance of fibro granular composite at low frequency due to higher flow resistivity. The probable cause of this phenomenon is due to the incorporation of rice husk grains as a compensation for the removal of moisture contents. The effective amount of the fiber diameter reduction, which has significant effect in the enhancement of low frequency sound absorption, has not been addressed yet. The study aimed to introduce this new concept of fiber diameter reduction amount in the formulation of the analytical approaches. The analysis of the variability of the fiber diameter after the industrial processing is investigated in this paper in terms of rigid frame Johnson-Champoux-Allard model. Finally the elimination of three major environmental problems which are noise pollution, environmental pollution and waste elimination is highlighted in this study.