Statistic characteristics of the acoustic field in the ASIAEX 2001 South China Sea experiment

Abstract

The internal wave is one of the primary causes for ocean variations in shallow water. The temporal-spatial stability of the sound channel may degrade in the presence of the internal wave. The statistical characteristics of the acoustic field, excited by a 400-Hz source in the ASIAEX 2001 South China Sea (SCS) experiment, are presented. The receiving array was at a distance of 31 km from the source. Time series data of signal intensity were obtained at individual hydrophones of a 16-element vertical line array, and temporal correlations were observed from May 2nd to May 17th. The temporal correlation scales are closely related to the internal wave properties. Strong internal waves, especially solitary wave packets (dnoidal internal waves, cnoidal internal waves, etc.), are principal contributors to the reduction of the temporal correlation scales. The signal temporal correlation length is simulated at different frequencies by using the oceanic data collected in ASIAEX 2001, especially its dependence on the amplitude, nonlinear coefficient, the dispersion coefficient, and the linear speed of the solition. It is found that the temporal correlation length is −1.1 power dependent on the signal frequency and −1.3 power dependent on the amplitude. It is also found that the temporal correlation length decreases with increasing nonlinear coefficient and linear speed, and decreasing dispersion coefficient. The relations between the parameters of the internal wave and the temporal correlation length obtained from the simulations are in agreement with the experimental observations.