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The airflow resistivity is a key parameter to predict accurately the acoustical properties of fibrous media. There is a large number of theoretical and empirical models which can be used to predict the airflow resistivity of this type of porous media. However, there is a lack of experimental data on the accuracy of these models in the case of multi-component fibrous media. This paper presents a detailed analysis of the accuracy of several existing models to predict airflow resistivity which make use of the porosity, bulk density and mean fibre diameter information. Three types of polyester (PET) materials made using regular PET, hollow PET and bi-component PET with a range of densities are chosen for this study. It is shown that some existing models largely under- or overestimate the airflow resistivity when compared with the measured values. A novel feature of this work is that it studies the relative performance of airflow resistivity prediction models that are based on the capillary channel theory and drag force theory. These two groups of models are then compared to some purely empirical models. It is found that the prediction error by some models is unacceptably high (e.g. >20–30%). The results suggest that there are existing models which can predict the airflow resistivity of multi-component fibrous media with 8–10% accuracy. [ABSTRACT FROM AUTHOR]

Structural parameters are critical for the final properties of fibrous materials. Three common parameters (i.e., porosity, thickness and average fiber diameter) of each fibrous material are simultaneously determined based on their air penetration behavior. The Ergun-type equation and the Kozeny-type equation, with the help of the optimization method, are applied to conduct the inverse characterization. The prediction performance of the equations is evaluated by comparing the given pressure drop and the values predicted by the Ergun-type and Kozeny-type equations. The inversely determined parameters are compared with the directly measured values. The results show that the Ergun-type equation and the Kozeny-type equation are suitable for various fibrous materials, including conventional nonwoven materials and nanofibrous membranes. The selection criteria of these two equations are provided based on the relation of pressure drop-airflow velocity and the prediction accuracy. The results also suggest that the Ergun-type equation's coefficients and the Blake–Kozeny–Carman constant of the Kozeny-type equation need to be determined for each material. The relative errors for most of the inversely determined parameters are reasonable. The findings indicate that the airflow-based method is feasible for fibrous materials. • A novel airflow-based characterization method for structural parameters determination of fibrous materials. • The structural parameters can be simultaneously determined. • The novel characterization method is able to accurately determine the porosity and thickness of nanomembranes. [ABSTRACT FROM AUTHOR]