Anything under 20 db(A) is considered silent for all intents and purposes, under 30 db(A) is a soft whisper. If a hdd is mounted correctly, the loudest part will be the vibration of those spinning discs, but that's assuming it's mounted correctly. All it takes is 1 screw to be ⅛ of a turn too loose, and the screw itself becomes the transmitter for the hdd vibrations, buzzing against the frame. My WD Black is non too quiet, never had been, but only on startup when it's subject to smart status checks. After that, it hums as normal for a hdd. You might have a dieing hdd, it's possible, but unless actual performance is affected, it looks to be more like something is just loose.