Abstract
Renewable wind energy has become an advantageous alternative. By the end of 2020, the total global offshore wind energy capacity has exceeded 35GW, growing more than 106% in the 5 past years, and the capacity has exceeded 6GW. It is estimated that by 2025, the global installed capacity of offshore wind energy will reach 100GW. In 2020, China's new offshore wind energy installed capacity exceeded 3GW, accounting for 50.45% of the world's new installed capacity and became the second-largest offshore wind energy market in the world. Offshore wind energy projects will produce noise pollution with different characteristics during the construction and operation stages, which will cause temporary or permanent damage to marine life to some extent. In this paper, the on-site survey of the underwater noise during the construction period of the second section of the Shapa offshore wind farm in Yangjiang, Guangdong. The survey was conducted on two days, and the measurements were carried out at different distances outside the wind farm. Time-domain waveform analysis and frequency spectrum analysis were performed on the data. The research in this paper can provide technical reference for environmental impact assessment of offshore wind energy projects, and has great application value. Through the analysis of the underwater noise characteristics of the offshore wind farm at different distances, the following results are obtained: Firstly, as the distance increases, the measured sound pressure values far away from the wind farm site are slightly smaller than those at the edge of the wind farm. Due to the multi-path effect, the duration of the acoustic pulse signal measured at the edge of the wind farm is shorter than that outside the wind farm. The noise power of piling at the edge of the wind farm tends to be stable, which has little impact on the apogee. Secondly, the sound pulse of piling causes the underwater noise sound pressure level at the edge of the wind farm to be generally higher than that at the site far away from the wind farm. With the distance increasing, the frequency of the sound pressure peak will be shifted. The noise intensity has the largest change in the frequency range of 0~1000Hz, and it has little impact when the frequency range is over 1000Hz. The underwater noise at the edge of the wind farm is greater than the underwater noise far away from the wind farm by a relatively constant value. Thirdly, as the distance from the wind farm increases, the frequency spectrum within the frequency range of 150Hz to 250Hz changes significantly. Fourthly, the wind farm has little impact on the nearby underwater acoustic environment during the construction period, and the impact range is small, which is not enough to damage the hearing of creatures near the wind farm. However, whether the noise has a long-term impact on the physiology and behavior of nearby marine organisms remains to be verified by further experimental studies.