Perhaps the most obvious is to improve precision, which really is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the center distance of the tooth mesh. Sound can be suffering from gear and housing materials as well as lubricants. 
In general, be prepared to pay out more for quieter, smoother gears.
Don’t make the mistake of over-specifying the engine. Remember, the insight pinion on the planetary must be able manage the motor’s result torque. What’s more, if you’re utilizing a multi-stage gearhead, the output stage should be strong enough to absorb the developed torque. Certainly, using a better motor than required will require a larger and more expensive gearhead.
Consider current limiting to safely impose limits on gearbox size. With servomotors, result torque is a linear function of current. So besides protecting the gearbox, current limiting also shields the electric motor and drive by clipping peak torque, which can be anywhere from 2.5 to 3.5 times continuous torque.
In each planetary stage, five gears are at the same time in mesh. Although it’s impossible to totally eliminate noise from such an assembly, there are several ways to reduce it.
As an ancillary benefit, the geometry of planetaries matches the shape of electric motors. Therefore the gearhead could be close in diameter to the servomotor, with the output shaft in-line.
Highly rigid (servo grade) gearheads are generally more expensive than lighter duty types. However, for fast acceleration and deceleration, a low backlash gearbox servo-grade gearhead could be the only sensible choice. In this kind of applications, the gearhead may be viewed as a mechanical springtime. The torsional deflection resulting from the spring action adds to backlash, compounding the consequences of free shaft movement.
Servo-grade gearheads incorporate a number of construction features to reduce torsional stress and deflection. Among the more prevalent are large diameter output shafts and beefed up support for satellite-equipment shafts. Stiff or “rigid” gearheads tend to be the most costly of planetaries.
The kind of bearings supporting the output shaft depends on the load. High radial or axial loads generally necessitate rolling element bearings. Small planetaries could get by with low-cost sleeve bearings or various other economical types with relatively low axial and radial load ability. For larger and servo-grade gearheads, durable result shaft bearings are usually required.
Like the majority of gears, planetaries make noise. And the quicker they operate, the louder they get.
Low-backlash planetary gears are also available in lower ratios. While some types of gears are generally limited by about 50:1 and up, planetary gearheads extend from 3:1 (single stage) to 175:1 or more, depending on the amount of stages.