Optimization of flat multi-layer sound absorber by using multi-objective genetic algorithm for application in anechoic chamber

In an anechoic chamber, the flat multi-layer sound absorber is cheaper, easier to install and less complicated in manufacturing than conventional wedge and pyramid absorbers. Therefore, design of the optimum flat multi-layer absorber which has minimum thickness is desirable. In this paper, the genetic algorithm has been employed as an effective optimization tool to determine flat triple layer porous absorber. To obtain a broader range of porous materials, combination of foam and fiber types is used. Theoretical and numerical method (finite element method specifically COMSOL Multi-physics version 4.4) have been used to investigate on the operation of sound absorption correspond to the multi-layer structure. In the first step, mathematical model is verified and finite element method, theoretical and experimental results are compared together for two different samples of structures which show appropriate matching. Furthermore to verify the operation of programmed genetic algorithm, the results obtained from the optimization of flat triple layer porous absorber are compared with others that show accuracy and efficiency of this method. The optimization results indicate that a flat triple layer porous structure can achieve results comparable with quality wedge type structure with overall thickness slightly smaller than a fifth of a wavelength at 80 Hz cut-off frequency.