Sea trial researches on extraction of propeller shaft frequency

Character extraction of underwater acoustic signals is premise of target recognition. Shaft frequency is considered as the most typical character of targets such as ships. Therefore, it can be used for target recognition. In this paper, it provided a method of extracting shaft frequency from DEMON (Detection of Envelope Modulation On Noise) spectrum of radiated noise from the targets. To verify the method was feasible, we processed two pieces of sea trial data from different ship. The result indicated that the shaft frequency calculated accorded with the real value.