Effect of the microscale of the nanofiber membranes on their sound absorption performance

Nanofiber membranes (NMs), fabricated via electrospinning of poly(vinylidene fluoride-co-hexafluoropropylene) solution, can effectively enhance the sound absorption coefficient (SAC) of porous materials with minimal mass and space requirements, making them appealing for aircraft noise reduction. The macroscopic property of a material is inherently influenced by its microscale, and therefore, this study investigates the effect of NM microscale on sound absorption and utilizes the transfer matrix method to reveal the effect of fiber diameter on the sound absorption of the membranes. The impact of the polymer concentration and solvent composition on the fiber diameter of these membranes is discussed. Experimental results demonstrate that alterations in solution parameters yield diverse fiber diameters and acoustic properties. An optimized polymer concentration and solvent composition for enhanced sound absorption are given through controlled experiments under specific stirring and electrospinning parameters. Notably, in the 1-2 kHz range, NM for melamine foam exhibits a 25% average increase in SAC, with 0.15% thickness and 0.02% weight increments. The Knudsen number and specific surface area are introduced to explain the variations in the SACs among NMs. This study provides insights into membrane acoustic properties at the microscopic level and offers guidance for producing high-performance NMs for sound absorption.