Helicopter Cabin Noise Reduction Based on Compounded Periodic Struts

To reduce the harmonic noise generated by gear meshing of the main gearbox, a novel compounded periodic strut for helicopter main gearbox is adopted, and its performance of vibration and noise reduction is characterized in this paper. The dynamic models of a single strut and the gearbox/struts coupling system are established based on the spectral element method firstly. Simulation results show that the periodic strut exhibits good abilities of broadband vibration attenuation, not only in the axial direction but also in the lateral and torsional directions. Also, a good broadband vibration isolation characteristic of the gearbox/struts coupling system is obtained with the new struts. Based on the helicopter model test system, experimental research is carried out. The effectiveness of the novel strut used for helicopter cabin broadband noise reduction is demonstrated by the experimental results, where maximum attenuations of measured fuselage vibration and cabin noise exceed 40dB and 30dB respectively in the frequency range from 300 to 2000 Hz.