Mid episode, we heard a loud bang and Carter started flipping out and barking! He almost never barks, same with Penny. Auggie was the barker of my trio.
I texted Dave, thinking it had been a firework nearby, and checked the Ring camera to see if there was anything untoward visible outside.
Then I realized something had probably fallen over, and after a quick look in the dining room -- where I found the toaster oven tray that I haven't been able to find for months, sitting on the base of a floor lamp -- and kitchen, I realized it might be the fan in the bedroom.
Sure enough! Good thing that didn't happen in the middle of the night, waking us all up! Wouldn't be likely to fall asleep again.