I just received my new MacBook Pro, which I bought online from Apple directly. When I turn on the computer, just before the familiar start-up tone, I hear a strange loud buzzing sound. It's kind of similar to the sound my old Mac makes after I turn in on from sleep-mode, but it's louder and harsher-sounding. It happens every time. It only lasts a second or two, then the start-up tone kicks in and the computer starts up normally. I've had various Macs in the past, and I always only heard one clean tone at start-up. Does anyone have a similar experience with a MacBook Pro or any advice as to what that may be? Should I send the computer back? Thank you so much!