Helical gears excite their housing system through forces and moments of bearings and then radiate noise. If noise is to be reduced, the contribution of noise to the gear housing due to the force and the moment must be determined. This work analytically investigated the radiated noise of a helical gear-housing system due to the excitation of helical gears. The helical gear-housing system consisted of gears, shafts, bearings, housings, and accessories. The gears were modeled as a 12-degree of freedom mass-spring-damper system; the shaft was modeled as a rod, a beam, and a torsional shaft so that the force and the moment were transmitted; and the gear housing was modeled as a clamped circular plate with viscous damping. The modeling of this system used transfer matrices for helical gears, shafts, and bearings. Damping for both the bearings and the plate were obtained by modal testing. An analysis of forced vibration of assembled transfer matrices produced a transmission of vibration. For the evaluation of noise, sound pressure from the plate due to the force and the moment in both radial and tangential directions was analytically derived by the Rayleigh integral. The analytical derivation and parameters from the experiment were applied to an analysis of noise for the two sets of helical gears with differing gear ratios. The analysis showed that the moment excitation in both helical gears contributed more to the noise of the plate than axial force excitation.

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