I notice that my ballast makes more noise than it used to or that I have one ballast that makes more noise than the other. How do I fix these problems?

The transformers in the ballast are made up of a series of metal plates that after time start vibrating apart or the bolts that bolt down the transformer vibrate lose. Try tightening all the bolts in the ballast. If the ballast still makes noise, then you need to run small bolts trough the holes in the top of the ballast and tightening them snuggly will pull the plates back together.