Perhaps the most obvious is to improve precision, which is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the guts distance of 
the tooth mesh. Sound is also suffering from gear and housing materials along with lubricants. In general, be prepared to pay out more for quieter, smoother gears.
Don’t make the mistake of over-specifying the electric motor. Remember, the input pinion on the planetary should be able handle the motor’s output torque. What’s more, if you’re using a multi-stage gearhead, the result stage should be strong enough to absorb the developed torque. Obviously, using a more powerful motor than low backlash gearbox required will require a bigger and more costly gearhead.
Consider current limiting to safely impose limits on gearbox size. With servomotors, result torque is certainly a linear function of current. So besides safeguarding the gearbox, current limiting also protects the electric motor and drive by clipping peak torque, which may be 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 get rid of 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. Hence the gearhead can be close in diameter to the servomotor, with the output shaft in-line.
Highly rigid (servo grade) gearheads are usually more costly than lighter duty types. However, for quick acceleration and deceleration, a servo-grade gearhead could be the only sensible choice. In such applications, the gearhead could be seen as a mechanical springtime. The torsional deflection resulting from the spring action adds to backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate several construction features to reduce torsional stress and deflection. Among the more common are large diameter result shafts and beefed up support for satellite-gear 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 can often get by with low-price sleeve bearings or other economical types with fairly low axial and radial load capacity. For larger and servo-grade gearheads, heavy duty result shaft bearings are often required.
Like the majority of gears, planetaries make sound. And the faster they run, 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 or more, planetary gearheads prolong from 3:1 (one stage) to 175:1 or even more, depending on the amount of stages.