I dunno guys…it might not be nothing -
If you’ve noticed a sudden change in the sound of the machine, you might want to check to make sure that the fan blades on the exhaust fan don’t need cleaning, both front and back side. If there is a build-up of resin, melted adhesive and gunk on the front of the fan blades, it can cause it to run out of balance, which does change the tone of the machine. (And can make it a lot louder.) Same for the grid behind the fan.
Be very careful cleaning the fan front, you go in through the open top of the machine. I used long Q-tips and gun-cleaning swabs, slightly moistened, and it took a couple of days leaning over the machine. Use a small flashlight so you can see what’s going on in there. Clean one blade and then manually rotate the next into place. (Obviously, make sure the machine is off while you are doing this.) Also be very careful not to push the gantry any farther forward at the front of the machine than it can normally reach during printing.
Cleaning the back is easy…take off the vent hose, vacuum out the junk and clean the grid with a small brush.
Doesn’t hurt to check. If they’re fairly clean, no problem…it’s just normal stepper sounds. Mine does sing to me with a lot of my designs.