A new method for the characterization of perforated facings using a wide frequency range Impedance Sensor

Perforated facings (like fabrics, micro-perforated screens, ...) are widely employed in noise reduction solutions. Following previous works, it has been shown that they can be described as a porous media with identical cylindrical perforations. Then, a classical five parameters JCA model can be employed to predict the acoustical behaviour of perforated facings and, due to their small thicknesses, these five parameters can be obtained from only two independent quantities: the perforation average radius and the perforation rate. The CTTM and LAUM have recently developed a new approach for the measurement of JCA porous model parameters. This approach relies on the properties of two innovative apparatuses: an Impedance Sensor which allows for accurate impedance measurements over a wide frequency range combined with a patented compact anechoic termination. These devices are used to propose an improvement of an existing method for perforated facings characterisation. By using a non-resonant acoustic load and the Impedance Sensor, an accurate estimation of facing bulk magnitude can be done over a wide frequency range. Then the possible impact of the facing vibrational mode and of the acoustic load resonances is reduced, allowing for a more accurate estimation of facing parameter. Results are presented and discussed for different samples.