Design of tunable low-frequency acoustic energy harvesting barrier for subway tunnel based on an optimized Helmholtz resonator and a PZT circular plate

This paper presents a tunable, low-frequency acoustic energy harvesting barrier, which contains the following four parts: the noise acquisition input module, the Helmholtz resonator optimization module, the resonant frequency tuning module, and the electricity generation module. The aim of this study is to make rational use of the huge noise energy inside the subway tunnel and convert it into electric energy to power the sensing and detecting equipment and lighting equipment along the railway. In this work, the optimal harvester unit and resonant frequency tuning part were pertinently designed to increase the output power of the unit. Experimental results show that one unit of the system can generate 317.5 mV instantaneous voltage and 100.8 μW instantaneous maximum power at 100 dB, and it verifies the efficiency and practicability of the proposed acoustic energy harvesting noise barrier. The device has a broad application prospect and can be adapted to different tunnel environments, including high-speed railway tunnels, highway tunnels, urban subway tunnels, etc., with excellent conversion efficiency. These results can provide valuable ideas for the design and practical application of new multi-functional noise barriers in the future.