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 materials as well as lubricants. In general, expect to pay out more for quieter, smoother gears.
Don’t make the error of over-specifying the electric motor. Remember, the insight pinion on the planetary should be able deal with the motor’s output torque. What’s more, if you’re using a multi-stage gearhead, the output stage should be strong enough to soak up the developed torque. Certainly, using a more powerful motor than necessary will require a larger and more expensive gearhead.
Consider current limiting to safely impose limits on gearbox size. With servomotors, output torque is definitely a linear function of current. Therefore besides protecting the gearbox, current limiting also protects the motor and drive by clipping peak torque, which may be anywhere from 2.5 to 3.5 times continuous torque.

In each planetary stage, five gears are concurrently in mesh. Although you can’t really totally get rid of noise from this assembly, there are many methods to reduce it.

As an ancillary benefit, the geometry of planetaries matches the shape of electric motors. Therefore the low backlash gearbox 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 quick acceleration and deceleration, a servo-grade gearhead could be the only sensible choice. In this kind of applications, the gearhead may be seen as a mechanical spring. The torsional deflection resulting from the spring action increases 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 load. 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 larger and servo-grade gearheads, durable output shaft bearings are often required.
Like the majority of gears, planetaries make noise. And the faster they operate, the louder they obtain.

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