Perhaps the most obvious is to increase precision, which is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the center distance of the tooth mesh. Sound is also suffering from gear and housing components in addition to lubricants. In general, expect to spend more for quieter, smoother gears.
Don’t make the error of over-specifying the motor. Remember, the insight pinion on the planetary 
must be able manage the motor’s output torque. What’s more, if you’re utilizing a multi-stage gearhead, the result stage should be strong enough to absorb the developed torque. Obviously, using a more powerful motor than necessary will require a larger and more expensive gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, result torque is definitely a linear function of current. So besides safeguarding the gearbox, current limiting also protects the 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 simultaneously in mesh. Although it’s impossible to totally remove noise from such an assembly, there are several methods to reduce it.
As an ancillary benefit, the geometry of planetaries fits the form of electric motors. Thus the gearhead could be close in diameter to the servomotor, with the result shaft in-line.
Highly rigid (servo grade) gearheads are usually more costly than lighter duty types. However, for fast acceleration and low backlash planetary gearbox deceleration, a servo-grade gearhead could be the only sensible choice. In such applications, the gearhead could be viewed as a mechanical spring. The torsional deflection caused by the spring action adds to backlash, compounding the consequences of free shaft movement.
Servo-grade gearheads incorporate a number of construction features to minimize torsional stress and deflection. Among the more prevalent are large diameter result shafts and beefed up support for satellite-equipment shafts. Stiff or “rigid” gearheads tend to be the costliest of planetaries.
The type of bearings supporting the output shaft depends upon the load. High radial or axial loads usually necessitate rolling element bearings. Small planetaries can often manage with low-price sleeve bearings or other economical types with relatively low axial and radial load capability. For bigger and servo-grade gearheads, durable output shaft bearings are usually required.
Like the majority of gears, planetaries make sound. And the faster they operate, the louder they get.
Low-backlash planetary gears are also available in lower ratios. Although some types of gears are generally limited by about 50:1 and up, planetary gearheads lengthen from 3:1 (one stage) to 175:1 or even more, depending on the amount of stages.