Predictive model of sound propagation in porous materials: Quantification of fiber nonwoven fabric by material density and fiber diameter

Many predictive models of sound propagation in porous materials require flow resistivity as a parameter. In the case of fibrous materials, flow resistivity varies with bulk density (by forming) and is not necessarily an efficient parameter. On the other hand, only the material density and fiber diameter of fibrous materials are the physical quantities that do not vary with a change in bulk density. If one of these physical quantities is used as a parameter, since it does not vary with a change in bulk density and its measurement is not necessary, the acoustic design work (optimization of the fiber mixing rate) of fibrous materials would become possible. In this paper, the relationships of the material density and fiber diameter of fibrous materials with the normal incidence absorption coefficient are clarified, and a new predictive model is shown.