Analysis of Sound Fluctuations in Shallow Water in High Sea States

Sound intensity fluctuation plays a significant role in underwater acoustic studies. In this article, an experiment was conducted in the South China Sea using a buoy system that autonomously emitted and received sound signals to obtain data on sound fluctuations under different wind conditions (in windy weather) for about 179 h. Results showed that the fluctuation of the transmission loss in a fixed position reached up to 15-20 dB. Different potential reasons for this transmission loss fluctuation are analyzed. Using the wind speed data provided by the Earth system, the sea surface wave spectrum model, and the bubble layer model, the fluctuation of the transmission loss was simulated based on the modified Ramsurf sound propagation model. The simulation and experimental results were in good agreement with each other. Therefore, the fluctuation of the transmission loss due to wind-generated waves in high sea states should be considered while studying underwater communication, particularly in shallow water with a positive gradient sound velocity profile.