Designing a low-noise gearbox by using sound-radiation analysis of a gear system

A method for predicting gear noise produced by a gear system was developed. This method calculates the distribution of sound pressure around the gearbox and identifies the areas from which noise radiates intensely. According to the sound-power level calculated from this pressure distribution, a low-noise gearbox was designed by adding ribs. The appropriate adding points were then calculated from the viewpoint of mass variation. It was found that to decrease the noise, ribs should be added in two places: (i) along the line with maximum curvature through the antinode of the gearbox's vibration mode or (ii) the minimum-length line which crosses the most contour lines through the maximum point of the sound-pressure contour map. It was also found that in the case of a gearbox with a vibration mode in which the gearbox side faces vibrate in opposite directions, noise can be effectively reduced by connecting the ribs on both side faces.