A non-parametric fluid-equivalent approach for the acoustic characterization of rigid porous materials

•Acoustic characterization of rigid porous materials by using a non-parametric methodology.•Use of a more general approach that overcomes some of the parametric models limitations.•A simple technique that uses only a reduced number of experimental measurements, avoiding complex equipment configurations.•Extensible methodology, easily adaptable to multilayer systems in order to characterize thin or light layers. The acoustic characterization of porous materials with rigid solid frame plays a key role in the prediction of the acoustic behavior of any dynamic system that incorporates them. In order to obtain an accurate prediction of its frequency-dependent response, a suitable choice of the parametric models for each material is essential. However, such models could be inadequate for a given material or only valid in a specific frequency range. In this work, a novel non-parametric methodology is proposed for the characterization of the acoustic properties of rigid porous materials. Unlike most widespread methodologies, this technique is based on the solution of a sequence of frequency-by-frequency well-posed inverse problems, thus increasing the characterization accuracy. Once a reduced number of experimental measurements is available, the proposed method avoids the a priori choice of a parametric model.