Inverse acoustic characterization of porous materials in impedance tube using genetic optimization

Diego Willian da Silva¹; Renato Barbieri¹

¹ UDESC - Universidade do Estado de Santa Catarina

doi:10.20906/CPS/CILAMCE2017-0814

Resumo

Porous materials such as foams or fibrous composites are widely used in several applications of noise control, thus the acoustic characterization of these materials is fundamental for an efficient application of resources. Several models have been developed throughout the years looking to acoustically characterize porous materials, usually these models depend on the physical properties of the material. In the model developed by Johnson-Champoux-Allard (JCA) a porous material can be modelled acoustically by five physical parameters: the porosity, the tortuosity, the flow resistivity and the viscous and thermal characteristic lengths. Due to the difficulty in measuring all the necessary properties to characterize the material, at least through the traditional methods, since it is necessary a specific test and apparatus to estimate each property, in recent years researches are being developed and alternative methods for obtaining these properties are being studied. A method that draws attention is the inverse characterization of the properties based on impedance tube measurements, this way it's possible to replace the traditional tests by a single test in impedance tube. The properties needed in the JCA model can be obtained through an optimization process. In this paper a reverse acoustic characterization of porous materials through an optimization process using the differential evolution algorithm is presented. The effectiveness of the presented method is evaluated through an experimentally validated virtual impedance tube numerical model. The experimental validation of the numeric model, which is done through standard samples measurements, is presented and the optimization process is explored and analyzed since the parameters can be controlled and are well known in the numeric model.

Palavras-chave: Acoustics; Porous material; Genetic optmization; Differential evolution; Impedance tube; Inverse characterization