The Characteristic Analysis Of Ambient Sea Noise At Dongsha Sea Area And Its Correlation Study With Wind Speed

Light and electromagnetic waves decay rapidly in seawater and the propagation distance is short. they are unable to meet human needs in ocean activities. Sound wave is the only energy of radiation that can propagate over long distances in the ocean. In the underwater target detection, underwater communication and navigation, sound wave is the only effective radiation in the ocean. Ocean ambient noise is an important acoustic parameter in the ocean. It disturb active sonar, limit passive sonar performance while containing a wealth of ocean information. It is also the important physical parameter for concealing submarine. Therefore, the study of the ocean ambient noise is of great significance.Based on the data of ocean ambient noise obtained from May 3, 2001 to May 17, 2001 in the South China Sea, The study of 50 Hz, 100 Hz, 200 Hz, 400 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, a total of 8 frequencies of shallow water ambient noise is given. This paper mainly includes the following aspects: 1. Review the significance of ocean ambient noise research and its domestic andforeign research progress; 2. Introduce the profile of Asian Seas International Acoustic Experiment in the SouthChina Sea, and the acoustic data that was obtained; 3. Introduce research theories and methods employed in this paper; 4. Use Matlab software to process the data of ocean ambient noise, analyse thetime-frequency characteristics of ocean ambient noise and observe variationcharacteristic of ambient noise level with time and frequency; 5. Analyse the correlation between ambient noise and sea surface wind speed;During the experiment there was a tropical storm. The surface wind speed has a sharp rise and fall in the process. Rainfall and the change of wave height lead to the changes in the ocean ambient noise. In this paper, we use the local wind speed data in the regression analysis of ocean ambient noise and sea surface wind speed. By using the change of sea surface wind speed during the passing of tropical storm and calculating the correlation coefficient between wind speed and ocean ambient noise level in different depths, the effects of wind speed on the ocean ambient noise are studied. By analysing the changes of the ocean ambient noise during one tropical storm day, the changes of the ocean ambient noise level with the wind speed is observed. In the end, the chn.15 hydrophone data were choosed for regression analysis between ambient noise and wind speed and for the correlation coefficient calculation between them. According to the linear relationship between ambient noise and logarithmic speed, the sea surface wind speed was retrieved, and the error shown.Research results show that: ambient noise level increases with the decrease of frequency, high frequency ocean ambient noise has a process of rise, and fall during the storm. In high frequency range, the correlation between ocean ambient noise level and sea surface wind speed is good. In the frequency range from 1000Hz~1250Hz,The correlation coefficient between them is between 0.4 and 0.5. When the frequency is less than 200 Hz, the correlation coefficient between the two is between-0.2 to 0.2. In this paper, the regression analysis for the ocean ambient noise and wind is performed. The error range is about 5%~20% when the sea surface wind speed is retrieved.Shallow water environment is complex, there are many factors that influence the ocean ambient noise. This research is just about the wind noise in the marine environment. The effect of tide, wave, ship and other factors on the marine environment noise remains to be studied in the future.