The intensity fluctuations and statistical characteristics in the shallow water at the north of South China Sea

Temporally integrated intensity and peak intensity of the ocean acoustic field are key factors in sonar system,while the sound field will be fluctuated caused by the internal waves in the ocean.The statistical characteristics of the fluctuated sound intensity is concluded based on the experiment data analyzation in the shallow water at the north of South China Sea with fixed source transmitter and sound receivers along with numerical simulation.It is shown that the fluctuation of the temporally integrated intensity is smaller than the peak intensity;the probability distribution functions of the temporally integrated intensity and peak intensity are close to the log-normal.The fluctuation of the temporally integrated intensity and peak intensity is associated with the source frequency.The fluctuation at the center frequency of 650 Hz is higher than the result at the center frequencies of 310 Hz and 375 Hz.For the same frequency,the scintillation index of the sound intensity increases as the source-receiver range increases when the ocean bottom is flat.The fluctuation of the sound intensity is more complicated when the sea depth become deeper as the source-receiver range increases at a fixed frequency.In this case,the scintillation index of the sound intensity increases at first and decreases after certain range as the source-receiver range increases.