Analysis of underwater transient signals and their detection by spectral correlation

The features of the transient signals produced by vessel are investigated using normalized short time spectrum. The survey covers 4 hour data recorded on the sea including 43-vessel noise. Some typical kinds of time-frequency distribution of passive transient signals are categorized. The spectral correlation (second order cumulant spectrum) is adopted to detect passive underwater transient signals. The analysis of 18 underwater transient signals demonstrates the significant processing gains. The last section of the paper analyzes the modes of these passive transient signals using spectral correlation. The modes-one mono, another triple and third penta are distinctively identifiable, presenting themselves as useful features in classification of transient signals.