| Abstract |
The ambient noise were measured on 3 SHRUs (Several Hydrophone Record Unit) of QPE (Quantifying, Predicting and Exploiting Uncertainty Initiative) Experiment in the North Mien-Hua Canyon in the summer of 2009, and 6 frequencies, which are 50, 100, 500, 1,000, 3,000 and 4,000 Hz, were analyzed in this study. NSYSU-SHRU was deployed on continental shelf at depth of 143 m by National Sun Yat-Sen University (NSYSU), WHOI-SHRU#1 and WHOI-SHRU#2 were deployed inside and outside of Northern Mien-Hua Canyon at depth of 126 m and 337 m by Woods Hole Oceangraphic Institution (WHOI). The fluctuations of NSUSY-SHRU’s ambient noise levels can be analyzed by Fourier analysis. With the similar analysis on temperature variation, the acoustic data has shown obvious K1 and M2 tidal periods. The frequency dependence of ambient noise was also investigated, the low (50, 100 Hz) frequency components were mainly contributed from distant shipping and strumming noise, and the local wind was the dominant factor in higher (500, 1000, 2,000 and 4,000 Hz) frequencies. The result was further verified by the increased levels at higher frequency due to the typhoon Morakot during the experiment. The probability distribution of ambient noise levels was calculated at each frequency, and was found the lower frequency ambient noise levels were significantly affected by the strumming noise of mooring, and the higher frequency ambient noise levels were significantly affected by the typhoon. Finally, we also investigate the difference between inside and outside of Northern Mien-Hua Canyon by WHOI-SHRU#1 and WHOI-SHRU#2, the low (50, 100 Hz) frequency components were mainly contributed from distant shipping and the masking effect by canyon terrain, the water depth was the dominant factor in higher (500, 1000, 2,000 and 4,000 Hz) frequencies, and the noise level inside of the Northern Mien-Hua Canyon is lower than outside for 6~14 dB. |
|---|
