The multi-local resonance metamaterial is based on the local resonance mechanism of resonators, effectively blocking wave propagation within multiple resonant frequency ranges, a phenomenon known as band gaps. In practical applications for vibration reduction, the goal is to achieve wide-band vibration attenuation at low frequencies. Therefore, this study aims to improve the vibration reduction performance of multi-local resonance metamaterials by lowering the band gap frequency and expanding the band gap width. To achieve this, an objective function was formulated in the optimization problem, considering both the frequency and width of the band gap, with the geometric shapes of the multiple local resonators selected as design variables. The Sequential Quadratic Programming (SQP) technique was employed for optimization. The results confirmed that the band gap was generated at lower frequencies and that the band gap width was expanded.

The design and implementation of acoustic metamaterials have garnered significant interest for their potential in noise and vibration reduction and control. However, the process of fabricating metamaterials is often perceived as challenging and confined to specialized fields. In this study, we aim to remove these barriers by demonstrating that it is possible to design and implement acoustic metamaterials using a simple array of commonly available PVC pipes. We designed and fabricated metamaterials using PVC pipe arrays and validated their performance through both numerical simulations and experimental testing. The experiments were conducted using standard audio equipment, and the results showed consistent trends with the numerical simulations. This research demonstrates that acoustic metamaterials can be effectively realized using accessible materials like PVC pipes, providing a practical approach to noise reduction and control.