Ok the "noise" I am talking about here is not noise in photos, it's actual small noise/sound coming from camera.
I have been using my camera for around 6 months, but never noticed this before. May be because I have been with people/outside. Last week I was sitting alone at home, and focusing on an object when I noticed small noise from sensor. The noise comes only when I half press the shutter button to auto focus, and stops as soon as I take off my fingers from button. The noise is like a computer fan..but not that loud of course. Should I assume this to be normal?