Perhaps the most obvious is to increase 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 in addition to lubricants. In general, expect to pay more for quieter, smoother gears.
Don’t make the mistake of over-specifying the motor. Remember, the insight pinion on the planetary should be able deal with the motor’s output torque. Also, if you’re utilizing a multi-stage gearhead, the result stage must be strong enough to absorb 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 low backlash planetary gearbox limitations on gearbox size. With servomotors, result torque is usually a linear function of current. Therefore besides safeguarding 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 at the same time in mesh. Although it’s impossible to totally remove noise from such an assembly, there are many ways to reduce it.
As an ancillary benefit, the geometry of planetaries matches the shape of electric motors. Thus the gearhead can be close in diameter to the servomotor, with the output shaft in-line.
Highly rigid (servo grade) gearheads are generally more costly than lighter duty types. However, for quick acceleration and deceleration, a servo-grade gearhead may be the only sensible choice. In this kind of 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 several construction features to reduce torsional stress and deflection. Among the more prevalent are large diameter result shafts and beefed up support for satellite-gear 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 can often manage with low-price sleeve bearings or various other economical types with fairly low axial and radial load capacity. For bigger and servo-grade gearheads, heavy duty output shaft bearings are 
usually required.
Like most gears, planetaries make noise. And the faster they operate, the louder they obtain.
Low-backlash planetary gears are also available in lower ratios. Although some types of gears are usually limited by about 50:1 and up, planetary gearheads expand from 3:1 (solitary stage) to 175:1 or even more, depending on the number of stages.