Optimized sonic crystals for enhanced bandgap in noise attenuation: design, fabrication and experimental investigation

Abstract

The application of Sonic Crystals (SCs) in the field of filtering and noise insulation has garnered increasing attention in recent years, but they often suffer from narrow and limited bandgaps (BGs). This study introduces a novel scatterer geometry within a square lattice with a lattice constant of 10 cm, designed to overcome the limitations of narrow BGs and limited frequency coverage. The innovative geometry is optimized using a genetic algorithm (GA) with three distinct objective functions to maximize bandgap characteristics, in terms of the summation of full BGs, bandgap coverage factor (BGCF), and fractional bandwidth (FB). In particular, a BG coverage of 370.6% in the frequency range of 0–6 kHz (achieved from the first optimization) and FB equal to 124.76% (achieved from the third optimization) show that our design is able to overcome the common limitations by generating multiple BGs across low, mid, and high-frequency ranges. Numerical simulations, confirmed by experimental validation, indicate the effectiveness of the optimized scatterer geometry in attenuating noise across the identified bandgap frequencies. Finite element method (FEM) predictions and experimental tests exhibit strong agreement and they verify the noise suppression capabilities of the SC across the wide frequency spectrum of 0 Hz to 6 kHz. This research presents remarkable results in terms of BG indexes and offers a significant contribution to the field of SCs compared to the existing literature on SC making it a strong candidate for future developments in acoustic metamaterials and noise reduction across a vast range of frequencies.