A comparison of analytical and optimization inverse techniques for characterizing intrinsic parameters of porous materials

摘要

In recent years, sound absorbing materials are finding many applications in transportrnIndustry. In automobiles they are used as noise control treatments in engine compartmentrnas well in passenger cabin. To understand and simulate acoustic behavior of these noiserncontrol treatments, intrinsic physical parameters are required. The acoustical behavior ofrnporoelastic material is governed by five macroscopic intrinsic parameters e.g. porosity,rnflow resistivity, tortuosity and characteristics lengths as well as three mechanicalrnparameters. Out of these five physical parameters, porosity and flow resistivity can bernmeasured directly by available standardized methods. But measurement of physicalrnparameters like tortuosity, viscous and thermal characteristic lengths is very difficult andrnno accepted procedure is available for their measurement. As an alternative, analyticalrninverse approach (mid-frequency) and optimization technique Genetic algorithm are wellrnknown in the literature. This paper compares the results from both techniques for intrinsicrnparameters. It also presents the effect of inverted parameters on sound absorption of thernporous materials using Johnson-Champoux-Allard model.