Expelair making loud noise

The expelair in en suite is making loud whirring noise,can anyone suggest what the problem is and how i can rectify it ??

It could be that it's blocked with dust/fluff and the fan is having a problem turning as a result. I had one making that racket, I unscrewed the cover and cleaned it out. Worked fine after that.

Safety First:
Before you open it .... make sure the power is off .... easily done at your fuse board.