Simulation research on the demodulation envelope shapes of vessel propeller cavitation noise

The demodulation envelopes of vessel propeller cavitation noise is a series of wave packets with basically similar shapes, almost equal intervals and a certain randomness in amplitude, moreover, these wave packets are in groups. The shapes of wave packets can directly affect the structures and shapes of the demodulation spectrums. By analyzing and comparing the demodulation envelope shapes of measured signals, it is shown that the shapes of wave packets can be divided into two types:smooth type and sharp type, and correspondingly, two simulation models can be set up:semi-sine wave model and Gaussian model. The test results of simulated and measured signals show that the semi-sine wave model can better simulate the characteristics of smooth envelope, and the Gaussian model can better simulate the characteristics of sharp envelope.