WD19S dock, pulsing fan noise

The fun of my WD19S 180W Dell dock keeps making pulsing noise all the time. Like starting fan at 100% and then to 0% after few seconds and repeating it. It does same even when notebook is off or unplugged from docking station. It is very annoying. Docking station is in the bedroom and keeps buzzing all the time, even when turned off.