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 is also affected by gear and housing components and also lubricants. In general, expect to spend more for quieter, smoother gears.
Don’t make the mistake of over-specifying the motor. Remember, the input pinion on the planetary must be able handle the motor’s output torque. What’s more, if you’re utilizing a multi-stage gearhead, the output stage must be strong enough to soak up the developed torque. Certainly, using a more powerful motor than required will require a bigger and more costly gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, output torque is certainly a linear function of current. Therefore besides protecting 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 at the same time in mesh. Although you can’t really totally remove noise from such an assembly, there are many methods to reduce it.

As an ancillary benefit, the geometry of low backlash planetary gearbox planetaries matches the shape 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 generally more expensive than lighter duty types. However, for rapid acceleration and deceleration, a servo-grade gearhead could be the only wise choice. In such applications, the gearhead may be seen as a mechanical springtime. The torsional deflection resulting from the spring action adds to backlash, compounding the effects of free shaft motion.
Servo-grade gearheads incorporate many construction features to reduce 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 have a tendency to be the costliest of planetaries.
The type of bearings supporting the output shaft depends upon the strain. High radial or axial loads generally necessitate rolling component bearings. Small planetaries could manage with low-cost sleeve bearings or various other economical types with relatively low axial and radial load capability. For bigger and servo-grade gearheads, durable output shaft bearings are often required.
Like the majority of gears, planetaries make sound. And the faster they operate, the louder they obtain.

Low-backlash planetary gears are also available in lower ratios. While some types of gears are generally limited to about 50:1 and up, planetary gearheads lengthen from 3:1 (solitary stage) to 175:1 or more, depending on the number of stages.