Underwater Acoustic Noise Characteristics of Shallow Water in Tropical Seas

In the underwater communication and target locating, the biggest challenge is to reduce the effect of underwater acoustic noise (UWAN). An experimental model is presented in this paper to characterize noise in the acoustic underwater channel in shallow water. Data is measured from different depths located in the Tanjung Balau, Johor, Malaysia. Most applications assume the UWAN as additive and Gaussian. However, the UWAN is not just thermal noise but a combination of turbulence, shipping and wind noises. Site-specific noise in shallow water often contains significant non-Gaussian components. Thus, it is appropriate to assume UWAN as colored rather than white with non-Gaussian probability density function (pdf). The real-time noise data are analyzed for different depths to determine the statistical properties such as power spectral density (PSD), autocorrelation function and pdf. The results show the UWAN has a non-Gaussian pdf, and is colored with a power spectral density that decays at a rate of approximately 20 dB/decade. Also, the power decreases with increasing depth as the distance from the surface at approximately 10 dB.