Underwater noise prediction and control of a cross-river subway tunnel: an experimental and numerical study

Low-frequency hydroacoustic noise and particle motion radiated from cross-river structures can pose a threat to aquatic systems, particularly for endangered species. In this study, an experimental study was first conducted to obtain the vibration and hydroacoustic noise of the metro tunnel of Nanjing Metro Line 10, which crosses Yangtze River in China. Then, a three-dimensional finite element model and acoustic model were developed to simulate the vehicle-induced vibration and underwater noise, respectively. Finally, the effect of reducing fastener stiffness on the vibration and noise reduction was investigated. The results showed that the measured dynamic responses agree well with the simulated results for the frequencies from 50 to 150 Hz. The metro vehicle-induced noise primarily occurred between 20 and 200 Hz, and the predicted sound pressure levels closely matched the experimental results. Both experimental and numerical noise levels exceeded the threshold of the Carassius auratus and Gadus morhua, which indicated potential impact of the noise on these species. Implementing lower stiffness rail fasteners proved effective in controlling the noise level and mitigating the impact on sensitive species. The proposed method was practicable in investigating the dynamic response of underwater tunnel and evaluating the influence of corresponding noise on aquatic species.