The accuracy of some models for the airflow resistivity of nonwoven materials

The airflow resistivity is a key parameter to consider when evaluating the acoustic performance of a fibrous material. The airflow resistivity is directly linked to a fibrous materials acoustic properties which allows for the non-invasive measurements of the fibre diameter and material density from acoustical data. There are several models that relate the airflow resistivity to the acoustic behaviour through the material's density and fibre diameter. It is not always obvious how accurately a model represents the true value of the flow resistivity of a nonwoven material with a fibre size variation. Therefore, the scope of this paper is to compare the performance of several theoretical and empirical models applied to a representative range of nonwoven fibrous media composed of blends of different fibre sizes and types. Being able to understand the performance of these models in application to fibre blends will enable users to characterise these types of fibrous media more precisely. From this work, it was concluded that the Miki model (Miki, 1990) is the most accurate model to invert the airflow resistivity from acoustical surface impedance of a wide range of nonwoven blends.