Statistic characteristics of the sound fields in the 2001ASIAEX South China Sea experiment

Abstract

Internal waves are one of the primary sources of ocean variations in shallow water. The temporal-spatial stability of the sound channel may degrade at the presence of internal waves. The statistical characteristics of acoustic signals transmitted by 400-Hz sources moored in the ASIAEX 2001 South China Sea (SCS) experiment are presented. The source was 31.3 km offshore from the receiving array. Time series data of signal intensity were obtained at individual phones of an 16-element vertical line array, and temporal correlations were observed from May 2 to May 17. The temporal correlation scales are closely related to internal wave properties. The largest internal waves, especially solitary wave packets (dnoidal internal waves), are the 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 of ASIAEX2001, as are the amplitudes, nonlinear coefficients, dispersion coefficients, and linear speeds 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 when the nonlinear coefficient <italic>α</italic> and the linear speed <italic>C</italic>₀ increase, and it decreases when the dispersion coefficient <italic>γ</italic> decreases.