Diagnose of noise fatigue sources of a helicopter

According to the wavelet transformation theory, a diagnose method for helicopters is established, including the order number of the wavelet decomposition and reconstruction, the noise signal decomposition, the separate signal reconstruction and 1/3 times frequency calculation. Since this method is with the high distinguishability for the low frequency signal and easy to reconstruct, it is fit for the noise signal separation of helicopter. By this method, the simulating noise signals are separated, and the separated signals are compared with the original signals, then it is found that the error between the separated signal and the original signal is lower than 2.3 percent. Moreover, on the basis of this method, the noise signals of the main rotor and tail rotor recorded from an AS350 helicopter are separated. It is shown that this diagnose method can be used to treat the non-stationary noise signals and separate the noise signals of the main rotor and tail rotor of the helicopter.