The Planetary Gears noise

In planetaries, noise is usually no worse, and often better than standard gear-and-pinion reducers. Having smaller gears means a lower pitch line velocity than a comparably rated pinionand- gear set. However, having a lot of identical planet teeth engaging at the same frequency with each input shaft revolution contributes to noise, especially at very high speeds. And the fact that these meshes occur in a circular orbit can make the situation more complex. Obviously, using spur gears of reasonably high quality couldn’t hurt. But helical gears, with their gradual rather than instantaneous tooth engagement, might be better for some operations.

Another noise reduction strategy that has been used involves designing the system so the planets mesh out of phase from one another and thereby provide a canceling effect. Damping the system can also help, as it discourages resonance.