Abstract: Offshore wind turbines continuously radiate low-frequency underwater noise during operation. Identifying the source mechanism and characterizing the propagation of the radiated sound field are fundamental to the assessment of the underwater acoustic environment and the protection of the marine ecosystem in operational sea areas. Based on 72 h synchronized measurements of pile vibration and underwater noise from the No. 66 W6.5F-185 wind turbine at the Donghai Bridge Offshore Wind Farm in Shanghai, this study clarified the regulatory effects of wind speed and rotor speed on the vibration characteristics of the pile foundation, and confirmed the high homologous correlation between underwater noise line spectra and structural vibration. On this basis, a data-driven finite element acoustic propagation model was developed on the COMSOL Multiphysics platform in a two-dimensional axisymmetric coordinate system, in which the frequency-domain spectra of the measured pile acceleration obtained via the Fast Fourier Transform (FFT) were adopted as the boundary excitation, enabling numerical simulation of the acoustic radiation process from the steel pipe pile into the shallow-water environment. Within the frequency band of 63-500 Hz, the sound pressure levels predicted by the model agree well with the measured values. The root mean square errors (RMSE) at the observation positions 30 m and 60 m from the pile are 3.75 dB and 3.50 dB under variable-speed operation, and 4.96 dB and 3.61 dB under constant-speed operation, respectively, all below 5 dB. The results demonstrate that the proposed method can simulate the shallow-water acoustic field during offshore wind turbine operation with satisfactory accuracy, providing an effective approach for the mechanism research and quantitative assessment of underwater noise from offshore wind turbines.