Metamaterials application on low-height noise barrier for railways: Challenges of real-world scenarios

Addressing noise in the living environment is essential to improving public health and urban quality of life. Railway noise poses significant challenges in densely populated areas, necessitating effective mitigation measures. This study explores using metamaterials to enhance the acoustic performance of low-height noise barriers (LHNB) for railways, focusing on geometrical constraints and environmental durability. Metamaterials offer tailored acoustic properties without increasing barrier size. However, their design is challenging, especially for low-frequency absorption, and outdoor conditions demand materials resistant to weathering and long-term degradation. Two acoustic metamaterials—Neck-embedded Helmholtz Resonators (NEHR) and channel resonators—are integrated into an LHNB to target noise attenuation across 100 to 5000 Hz. NEHRs are optimized for low-frequency performance, while channel resonators provide broader frequency absorption with tailored geometrical designs. These elements ensure a lightweight, compact solution without compromising acoustic efficiency. Analytical models and numerical simulations are validated experimentally to demonstrate the efficacy of this hybrid approach. Results highlight significant noise reduction while maintaining structural and aesthetic feasibility. This work advances the design and optimization of acoustic metamaterials, offering practical, scalable solutions for sustainable noise control in urban and transport environments.