Propagation Research Of Offshore Wind Farm Underwater Noise

In recent years, as the earth’s fossil resources dry up and the environmental protection consciousness of human increasing constantly, people began to attention in the development of clean energy, and wind power is an important part of clean energy, our country is located in the tropical and subtropical monsoon climate zone, wind resource is very rich, has a big development potential. The Chinese government have issued several relevant policy,vigorously promote the construction of offshore wind farm, offshore wind farm is more and more become an important part of our country energy map. But the wind farm radiates a lot of underwater noise during construction period and operation period, damages to the marine environment and marine in aquatic organisms, current research for offshore wind farm noise propagation is insufficient, so the research in this area is very necessary.In order to protect the Marine environment and Marine life, we must to monitor the underwater noise during construction period and operation period of offshore wind farm, analyze characteristics of underwater noise, analyze of the noise propagation attenuation characteristics, analyze the effect of noise transmission range, and put forward corresponding prevention measures.Main content of this paper are as follows:1.This paper introduces the general situation of the development of offshore wind and sea wind motor structure, the underwater sound propagation model and the research progress of during construction period and operation period of the offshore wind farm are introduced, and the noise sensitivity characteristics of marine biological research progress are reviewed.2.The underwater noise data acquisition system are introduced, the relevant data processing software are introduced, and matlab is introduced in this paper, using the method of data analysis: short-time Fourier transform method and Welch power spectrum density estimation method.3.This paper introduces the construction process of pile driving, the noise sources are analyzed during construction period,the noise source strength of target wind turbine is 236dB(re 1μPa)and has calculated the noise spectrum source level of target wind turbine.it is concluded that during the construction of the source information, uses the model to simulate and analogy analysis method for the prediction study conducted for the piling noise level during the construction of other noise, it is concluded that the safe distance of the corresponding marine conservation biology, that is selecting 500 m as a warning to the marine mammal behavior interference area and selecting 2500 m as a drum fish families safe distance.4. The noise signals of the octave band sound pressure level, power spectrum and peak sound pressure level are calculated by the acquisition of offshore wind farm project operating period and background noise data. The underwater noise source strength of target wind turbine is 144.4dB(re 1μPa).Frequency domain characteristics and power density spectrum characteristics research of offshore wind farm engineering area underwater noise are carried out through these data,on the basis, using Kraken model and Bellhop model, the propagation of wind farm operation periods underwater noise in horizontal and vertical distance is simulated and the degree of noise attenuation in different frequency bands is predicted, results show that the different simulation results under different frequency attenuation trend is a big difference and obvious multiapproaches interference phenomenon. The noise propagation models are verified by the measured data and the adaptive frequency range of two models is obtained(Kraken model is suitable for below 500 Hz, the Bellhop model that applies to more than 500Hz). The presence of background noise could affect the accuracy of the prediction.