Hey all. I bought my rMBP last week, and it's really an amazing machine. I just noticed that if I dim the display brightness down about 3/4 of the way, the screen starts to emit a high pitched humming noise. It get's louder as the display gets dimmer... Also, whenever the keyboard backlight is on, there is a similar high pitched buzzing noise at all levels of brightness. Just wondering if anyone has experienced the same thing, and if this is normal behavior? Thanks for the help!