In fact I did have the driver's door open when this was happening. It could be the same tone/buzz as the when leaving the key in the ignition...

Just prior to this, my ABS/ASR light came on and the ABS was not working. For codes, I got the usual #1 no fault found. I erased the code. While doing all of this, that was when I noticed this brief buzz. It's been raining up here for the past two-days.