Experimental and Statistical Energy Analysis of the Structure-borne Noise in a Helicopter Cabin

In this work, the mechanical power transferred from the main gearbox to the cabin of a helicopter is obtained experimentally and used as an input to the vibroacoustic model of the fuselage for interior noise prediction. The estimation of the transmitted mechanical power is based on the experimental evaluation of the coupled mechanical mobility and in-flight accelerations measured at the points connecting the main gearbox to the fuselage, i.e. the antitorque plate and struts. The predicted values, together with the airborne noise sources (upper deck cavity noise and aerodynamic excitation due to the turbulent boundary layer on the fuselage skin) are then fed into the vibroacoustic model of the fuselage/cabin, which is obtained using a Statistical Energy Analysis (SEA) approach. The reliability of the approach is finally demonstrated by comparing the SEA simulation results and in-flight noise measurements in terms of sound pressure level in the passenger cabin compartment.