Servo noise can cause a range of problems.
Electrical noise in the sense of variations in voltage or current can interfere with feedback and generally confuse the systems. Dirty electricity can create real problems, but there is always some noise in any electrical system. Using the right cables and using them correctly can help with electrical noise.
Humming, buzzing, chattering, and whining usually tell you that there are some imperfections in your servo or the related systems. Dirt — not dirty electricity but literal dirt — can cause noises like these. So can bearings that need maintenance. Remember, your maintenance free Rexroth machinery came with bearings packed in grease. They have a life expectancy of about ten years, and so did the components they belong to. If you use your servos for twenty or thirty years, those maintenance-free bearings will need replacing.
Then there are the big noises: shearing, gulping, or even weirder noises coming from your servo can help us diagnose your servo problems over the phone. Often we’ll hear the sound and know immediately that you’ve got configuration problems, for example.
The problem is, servo noise can start small and build up gradually. You get used to it. It’s just a little humming or whirring sound. Maybe over time it becomes an ungodly screeching noise, so you get earplugs for the whole team.
Instead, use the information from the noises to diagnose the problem. Then… fix the problem. This is much more effective than getting accustomed to the noise.
Factory reman is often the best solution for servo noise issues. All wearing parts will be replaced — that covers the bearings, for example, and anything that might have worked its way loose and started jiggling. The entire motor will be rebuilt, closed, and relaquered. Your servo will return to you in like-new condition, or even better.