Characterization of porous acoustic materials

Walter Lauriks (1) , Laurens Boeckx (1) , Philippe Leclaire (1)

1 LATF - Laboratorium voor Akoestiek en Thermische Fysica

An overview of the models and parameters of the acoustic wave propagation in porous media is presented. The most common parameters (the porosity, the permeability or flow resistivity and the densities) can be measured with standard methods. Ultrasonic methods for measuring the other parameters (the tortuosity and characteristic lengths) related to the complex pore micro-structure are reviewed. The ultrasonic methods are based on the transmission or reflection of airborne ultrasonic waves and on the signal analysis in the frequency and/or in the time domains. Ultrasonic scattering is discussed at higher frequencies where the classical models are no longer valid. In order to complete the characterization of porous acoustic materials, new techniques for evaluating the elastic and viscoelastic properties are proposed. These techniques are based on the generation of standing waves in a layer of material and on the spatial Fourier Transform of the displacement profile of the upper surface. Two configurations are proposed: a layer of porous material glued on a rigid substrate and a porous layer under Lamb conditions. Theoretical dispersion curves are fitted to the experimental results and this procedure can provide information on the complex shear modulus and of the complex Poisson ratio in a wide frequency range, typically between 50 Hz and 4 kHz.

Domaines: Acoustique [physics.class-ph]

Walter Lauriks, Laurens Boeckx, Philippe Leclaire. Characterization of porous acoustic materials. SAPEM 2005 Symposium on the Acoustics of Poro-Elastic Materials, Dec 2005, Lyon, France. ⟨hal-01329870⟩