Abstract
Nanofiber-porous systems comprising porous substrate overlaid with nanofiber weave offer potential for higher acoustic absorption than the substrate alone with negligible increase in thickness. The characterisation of nanofibers from acoustic measurements is investigated in this work and a regression model for predicting their acoustic properties from physical parameters is proposed to enable the design of nanofiberporous systems directly from fabrication parameters. Characterisation as a resistive screen via lumped element and Johnson-Champoux-Allard (JCA) models for transfer matrix representation of nanofiber-porous systems gave predictions of absorption coefficient that agreed strongly with measurement. The lumped element model was defined by less parameters and did not require nanofiber layer thickness measurements with the associated uncertainty, hence a regression model for lumped element parameters versus areal density was used to establish a design tool based on a single, easily measured physical property. This allows for optimised absorption at target frequencies without prior acoustic characterisation of the nanofiber layer, enabling analysis of complex acoustic networks incorporating nanofiber-porous systems. Disparities in flow resistance from physical measurement and acoustic characterisation were discussed in comparison with prior work and practical aspects of applying adhesives at the nanofiber-porous interface as well as electrospinning directly onto the substrate were found to impact acoustic performance, highlighting key considerations for largescale manufacturing. Measurements of transmission loss for various silencer configurations with nanofiber-porous systems agreed well with finite element simulations based on the material parameters derived from the acoustic model.