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In this paper, a promising acoustic structure for noise reduction was prepared, in which microperforated nanofibrous resonant membrane together with nonwovens were used. The role of microperforated nanofibrous film, the effect of perforation parameters, cavity and the assembly sequence of the composite fibrous structure on sound absorption performance has been studied. This structure effectively combined the porous sound absorbing, micro-perforated absorbing and membrane resonance mechanisms, which can improve the sound absorbing performance without weight and thickness penalty offering a competitive advantage in noise reduction. In addition, the composite materials exhibited favorable performance in a wide-frequency regime under the condition of appropriate assembly sequence and perforation parameters. [ABSTRACT FROM AUTHOR]

This work aims to obtain efficient sound absorbing materials in the low and middle frequency. Jute fiber and polypropylene were used to prepare a kind of composite material by mixing-hot pressing process. On this basis, micro-perforated composite materials with various perforation characteristics were fabricated. The effect of drilling diameter, punching ratio, thickness and cavity depth on its acoustic performance was studied. The acoustic-electric analogy model and transfer matrix method of the micro-perforated plate were introduced for analyzing the agreement between the theoretical value and the corresponding experimental results. It was found that the jute fiber reinforced polypropylene microperforated composite had good sound absorbing ability at the low and middle frequencies, and thus had obvious advantages compared with the traditional sound absorption materials. In addition, by properly adjusting the structural parameters, the materials can absorb broadband noise in different frequency ranges to meet diversified needs. Yet with such natural advantages, the microperforated composite we prepared could be promising alternatives in the noise reduction field. [ABSTRACT FROM AUTHOR]

A flexible micro-perforated material was fabricated for acoustic application in this study, which is different from the traditional perforated material whose general impression is rigid, dense and inflexible. The raw material is polyvinyl alcohol and develop into PVA nanofiber membranes by electrospinning. On this basis, flexible PVA micro-perforated membranes were fabricated through punching process. The structure combined nanofiber, porous material and perforated panel in an organic whole. And the effects of perforation rate, perforation diameter and cavity distance on the acoustic performance were studied in light of the experimental result. The acoustic-electric analogy model of the micro-perforated sound absorber was used for theoretical calculation and compared with the corresponding experimental results. As we studied, the flexible microperforated material had favorable sound absorption performance both in low and high frequency, which was a significant improvement over traditional perforated plate. Besides, the broadband sound absorption could be obtained with the properly selection and optimization of the structural parameters. These latent qualities of the flexible PVA micro-perforated membrane make it ideal for use in the noise reduction field as a flexible and lightweight acoustic material. [ABSTRACT FROM AUTHOR]