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This paper investigates the noise profile of modern railway systems and introduces a sound-absorptive precast modular block comprised of multiple materials and volumes. The components and configurations are selected in a specific manner such that each volume of material has a sufficiently different and complimentary sound absorption profile. The resulting system provides better overall sound absorption of railway noise while targeting specific frequencies of interest (typically low frequencies). The effectiveness of sound attenuation requires the railway noise to transmit through the outer volume material and into the inner volume material. Practical and environmental considerations require materials that can be utilized in large-scale manufacturing operations and result in a modular system that is price-competitive, relatively light-weight, easy to install, durable, and made from recycled materials.
Figallo et al. (Sun,) studied this question.