An inverse method to characterize fibrous sound absorbing materials.

Abstract

Characterization of sound absorbing materials is needed to predict its behavior. The most commonly used models to do so consider the flow resistivity, porosity, and average fiber diameter as parameters to determine the acoustic impedance and sound absorbing coefficient. Besides direct experimental techniques, numerical approaches appear to be an alternative to estimate the material’s parameters. In this work an inverse numerical method to obtain the porosity, the fiber density, and the fiber average diameter of a fibrous material is described. Using normal incidence measurements of the sound absorption coefficient and then using the model proposed by Voronina, subsequent application of basic optimization techniques allows one to characterize a sound absorbing material. The numerical results agree fairly well with the experimental data.