A new polyhedral sonic crystal for broadband sound barriers: Optimization and experimental study

In this research, a new polyhedral geometry for a 2D unit-cell with ultrawide frequency bandgaps is proposed. The genetic algorithm is combined with the finite element (FE) model to obtain an optimal geometry of the unitcell based on the two objective functions: (i) the largest bandgap within 0-1500 Hz and (ii) the largest bandgap summation in the range of 0-6000 Hz. Frequency analysis is conducted for the optimized geometries to illustrate the performance of the sonic crystal for the noise attenuation in bandgap frequencies. In order to validate the numerical results, an experimental test for a 3D model is designed and implemented. It is shown that a strong correlation is observed between the results from the bandgap diagram, frequency analysis, and experimental measurements. The proposed design presents a fractional bandwidth (FB) of 80.69 % and a bandgap coverage factor (BGCF) of 179.01 % in the applied frequency range, which are remarkable results in terms of bandgap indexes compared to the available literature of sonic crystals. The proposed design for unit-cell represents highly promising properties as a candidate for the noise control applications at both low and high-frequency ranges.