Changes in the sounds that it makes when it’s running can indicate a dirty fan. Buildup of resins and debris on the front of the fan blades can make it run out of balance.
There are a couple of methods for cleaning the exhaust fan here:
The first link in there is the recommended Glowforge procedure. You’ll need to buy a can of the solvent cleaner they recommend using. (The rest of the writeup is the way that I do it.)
