Underwater targets detection using interference spectrum

The underwater sound radiated by vessels consists of deterministic mechanical sounds, propeller noise and hydrodynamic noise. Though many methods have been done to control the sound radiated by vessels, flow noise is always present around a moving vessel. Time-frequency analysis is often used as a method to observe energy distribution of ship noise. In the time-frequency distribution picture of surface ship noise, parabolic patterns are evident. They are caused by multipath transmission of vessel noise. In the paper, using interference spectrum for target detection is discussed. And the superimposed interference pattern is utilized to find moving vessel range. Finally the speed and the closet point of approach estimation of a moving vessel is given using the method.