My XPS 13 2-in-1 7390 just started making a rapid beeping sound, which can be heard here. I don't believe this was anything to do with software, as I muted the speakers and it still continued, and it took a fairly long time into the shut down sequence (right until it fully turned off) for it to stop, so I have concluded that it is a hardware issue. I did have it plugged into a number of devices when the problem started (HDMI, DisplayPort, a couple USB devices, power, Ethernet, all via a thunderbolt hub), but it continued even when I unplugged it. The computer did not feel particularly hot when this happened. This has never happened before.

Any ideas?