The noise is "lethal" to your floppy drive. That is mold as dlfrsilver mentioned. Once you hear it IMMEDIATELY remove the disk from the drive. I have ruined many drives with this shit.
Crack open the disk and clean it as he said. Personally I just used water, not alcohol. Then place it in a NEW case, the old one probably has mold in it and you shouldn't use it again. You shouldn't just try to clean from the disk shutter because the mold in the case will get back on the floppy surface.
I restored MANY floppies with this method.