Perhaps the most apparent is to increase precision, which low backlash gearbox really is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the center distance of the tooth mesh. Sound can be suffering from gear and housing materials and also lubricants. In general, be prepared to pay out more for quieter, smoother gears.
Don’t make the error of over-specifying the electric motor. Remember, the input pinion on the planetary should be able handle the motor’s output torque. Also, if you’re utilizing a multi-stage gearhead, the output stage must 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 limits on gearbox size. With servomotors, result 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 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 eliminate noise from such an assembly, there are many methods to reduce it.

As an ancillary benefit, the geometry of planetaries matches the form of electric motors. Thus the gearhead could 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 fast acceleration and deceleration, a servo-grade gearhead could be the only wise choice. In this kind of applications, the gearhead could be viewed 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 many construction features to reduce torsional stress and deflection. Among the more common are large diameter output shafts and beefed up support for satellite-gear shafts. Stiff or “rigid” gearheads have a tendency to be the most costly of planetaries.
The type of bearings supporting the output shaft depends on the strain. High radial or axial loads usually necessitate rolling element bearings. Small planetaries could get by with low-cost sleeve bearings or various other economical types with fairly low axial and radial load capacity. For bigger and servo-grade gearheads, durable result shaft bearings are often required.
Like most gears, planetaries make sound. And the quicker 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 and up, planetary gearheads expand from 3:1 (one stage) to 175:1 or even more, depending on the number of stages.