The beeping sounds calling for SOS are normal. Apple has a set of guidelines for the 3 different type of beeping they have for Macs. The SOS beep means bad logic board. Screens also flick with the beeps.
Since Apple sent you a box, it most likely means a replacement or a logic board change.
"Danger, leprechauns."
Remember when Macs would play taps if there was a hardware failure?