Acoustic investigation on a sustainable and ventilated sonic crystal barrier for environmental noise absorption

Sonic crystal (SC) structures have emerged as a promising solution for mitigating low-frequency environmental noise in densely populated areas, owing to their subwavelength dimensions and superior multifunctionality, including air ventilation and noise blocking. This study presents a novel design of locally resonant SC structures based on the generalized Snell's law, enabling simplified optimization with predetermined lattice configurations. While such periodic structures exhibit high-efficiency sound shielding through reflection at specific resonant frequencies, their limited broadband sound absorption has restricted widespread application. To address this limitation, an antisymmetric Matryoshka-type unit cell design, combined with several accessible recycled materials as absorptive elements, has been proposed and optimized for improving broadband sound absorption in the low-frequency range around 800 Hz. Finite Element Method simulations followed by experimental measurements of transmission loss were employed to identify the optimal combination of the above-mentioned materials. The results demonstrate peak noise reduction exceeding 18 dB at locally resonant bandgaps, alongside significant broadband noise absorption achieved through the incorporation of sound-absorbing materials. The sustainable feature of the composite SC structures would benefit residents by facilitating wastes recycle and reducing noise pollution, resulting in an enhanced living environment.