I was in bed reading some news on my SP2 and noticed a faint electrical buzzing sort of sound coming from my SP2. I then put my ear to the rear of the SP2 and could hear the buzzing very clearly. I left it turned off (full shutdown) for a day then turned it back on but the buzzing is still there. Any one else noticed this with their SP2? Should I be worried? Would this sort of issue be covered under warranty? It was purchased from the MS store.