Improved sound absorption performance of synthetic fiber materials for industrial noise reduction: a review

Sound absorption mechanism, material modification and structural design of various synthetic fiber materials for industrial noise reduction are reviewed in this paper for the problems of low sound absorption coefficient (SAC) and narrow frequency band of porous materials. Delany-Bazley model and Johnson-Champoux-Allard (JCA) model are widely used to predict the SAC, but they are slightly different. The air viscous effect plays an important role in Delany-Bazley model and its modified forms, while JCA model and its modified forms consider the effect of thermal conduction in addition to air viscosity. In addition, synthetic fiber materials such as polymers, metal fibers and inorganic fibers are widely used in noise reduction fields of various industries due to their unique acoustic and mechanical performance. Acoustic properties of polymers are usually improved by adding fillers, using perforated structures, gradient porous structures, and multilayer composite structures. And improving preparation method, increasing thickness of back cavity, combining different pore sizes, developing new composite materials, and adopting perforation technology can greatly promote the engineering application of metal fibers in extreme environments. Common methods to improve the sound absorption performance of inorganic fibers are to modify preparation method, increase thickness of materials and research composite materials.