Cabin Noise Analysis and Noise Reduction Design of the Helicopter with Double-Swept Rotor Blade

The double-swept rotor blade is a new type of blade, and its vortex interference noise level is lower than that of traditional blade. In this paper, the contribution of the cabin noise source of a helicopter is analyzed, and the main gear box vibration and rotor aerodynamic noise are determined to be the main sources. The alternating load at the hub center with double-swept rotor blade is calculated. The vibration load information of the main gear box and the rotor aerodynamic load is predicted. Then the noise level in the cabin is analyzed by the acoustic boundary element method. The result shows that the sound pressure level at passenger’s ear is 131dB in the cabin without interior trimming. The skin is determined to be the key structure affecting the cabin noise by the analysis of plane acoustic contribution. After that, four skin structures are designed and their noise reduction effect is analyzed. The metal honeycomb sandwich skin structure has the best noise reduction effect, which can effectively reduce the cabin noise by 10.6%.