Simulation, measurement and optimization of sound absorption in gradient impedance fiber-based composites

In order to achieve effective noise absorption by finite thickness fiber-based materials, fiber-based composites integrating porous, resonant and damping structures were prepared in this research. Here, the effects of gradient structure, number of constituent units, nonwovens thickness and micro-perforated membrane fabric (MPMF) arrangement on the noise reduction of the composites were simulated and measured. The results showed that the gradient fiber-based composite has excellent broadband sound absorption effect. Moreover, designing the arrangement of micro-perforated structures in the composite can further improve its noise reduction coefficient (NRC). The fiber-based composite (thickness of 1.34 cm) designed by the algorithm has an NRC of 0.51, which is much higher than other noise reduction products with the same thickness. The multi-layer fiber-based composites have the advantages of strong noise reduction capability, small thickness, simple processing and low manufacturing cost, which can be flexibly applied in various noise reduction fields.