Experimental and numerical investigation of the structure-borne noise transmitted from the gearbox to fuselage of a helicopter

In order to predict the interior noise level of a helicopter using the Statistical Energy Analysis (SEA) approach, the mechanical powers transmitted to the fuselage by the main gearbox are needed as external inputs to the vibroacoustic model. In this work, the power values were estimated experimentally from the mechanical mobility at the fuselage attachment points and in-flight acceleration measurements. The experimentally-obtained dynamical powers were then applied to the SEA model at the connecting points between the main gearbox to the fuselage, i.e. the antitorque plate and struts. The good correlation of the SEA model with testing results in terms of sound pressure level in the cabin proved that the numerical-experimental methodology is reliable and can therefore be used for current and future design of Leonardo helicopters.