Multi- density inversion characterisation method for fibrous material

This paper describes a novel inversion methodology for determining the transport parameters of the Johnson- Champoux-Allard (JCA) equivalent fluid model, developed to provide a quick and easy-to-implement characterisation tool. The proposed approach, based on an optimisation algorithm, requires only the experimental evaluation of the normal incidence sound absorption coefficient on fibrous material samples, prepared from loose fibres, at various compression ratios. Unlike existing inversion methods, the proposed approach links the variation of transport parameters to changes in the material’s apparent density. The validation presented in the paper considers experimental data measured on two types of fibres: hemp fibres and glass fibres. Validation of the proposed method shows good agreement with well-established techniques and demonstrates its effectiveness across a broad range of fibrous materials.