Inverse methods of determining the acoustical parameters of porous sound absorbing metallic materials

Porous metallic material has become a kind of typical multifunctional material with the quick development of advanced manufacturing and forming process technologies in past years. At present, it has also been a structural function material with the characteristics of ultra-light weight, high specific strength and rigidity. As a sound absorbing material in noise control engineering, the acoustical parameters of porous metallic materials, especially such as the sinuosity factor, viscous and thermal characteristic lengths, are relatively difficult to obtain directly from the measurements under the common experimental conditions. On the contrary, the sound reflection and absorption coefficients,and the normal surface acoustic impedance of porous metallic materials are easy to exactly measure in a standard acoustic impedance tube. As a result, this paper introduced the inverse methods in order to determine the acoustical parameters of porous metallic materials based on available sound absorbing models such as Johnson-Champoux-Allard model, Biot-Allard model, etc. Moreover, inverse methods based on Taboo search algorithm (TSA), simulated annealing genetic algorithm (SAGA) and linear regression (LR), were developed; by which the main acoustical parameters of some porous metallic materials were found out for use elsewhere as well. Finally, the results from the different inverse methods were in comparison with each other to validate the effectiveness of the aforementioned inverse algorithms.