When i first got my MacBook a little over a month ago i remember it being pretty quiet but in the past week i noticed a constant blowing sound coming from it. It's really annoying specially when i want to work in silence, sometimes i have to turn on iTunes to block out the noise with music. I'm pretty sure it's the fan, but why would the fan be making such noise when it's running at a normal 1800 rpm and the CPU is around 45 degrees. Sometimes it seems to get louder too, and the fan is still at a normal rpm. Should i be worried? Should i take it in to the Apple store?