A preliminary numerical analysis of the noise radiated by a gearbox

The noise spectrum generated by a gearbox is characterised by harmonics which depend on the geometry of the gears, their rotational speed, possible axis eccentricity and imperfections of the teeth surface. The experimental investigation of the gearbox noise emission is a complex task, especially due to the difficulties in separating its contribution from the overall noise generated by other machineries of the testing train. Conventional laboratory tests evaluate the condition of full speed and no load, which is not representative of a realistic scenario, where the gearbox is subjected to a torque provided by the machinery it is connected to. This paper presents a numerical approach to predict the noise radiated by the gearboxes, through a multibody analysis in the time domain combined with a vibroacoustic analysis in the frequency domain using the boundary element method (BEM). The study investigates the influence of the rotational speed and the resisting torque on the radiated sound power. The results show that an increment in the rotational speed affects the position and magnitude of harmonic components, while an increment in the applied torque has a significant impact only on the magnitude of the radiated noise.