I just bought a new retina 13 this afternoon, I use the mac to work in a very silent room, I just realised that my new macbook has a very high pitch noise everytime I put the brightness in the lower level (1-3 brightness level), is that normal? the noise came from the keyboard, in particular the key a,s,d,w, and key 7,8,9,0. If i out the brightness level higher, the noise decrease, and no noise in the highest brightness level. Please advise me about it, since if it is not normal, i will return the product and get a replacement. an also, just now i notice that there is a continuous noise, like a moving hard disk in key g,h,j,k area, what i know is mac does not have any moving part except the fan, so where the noise come from???