Another one of the weird things that freak you out for a bit just happened to me.
I’m Working from home today suddenly I hear a clear, loud, BWUUUUUUUUUUUUM. BWUUUUUUUUUUUUM, BWUUUUUUUUUUUUM. It sounded like an alarm of some sort, but I can’t think of any alarm that is sounds like. So I quickly run outside, but it is definitely coming from inside. But then after about 20 seconds it stops, with no cause having been located.
A bit confused and on edge, I went back to work. About half an hour later it happened again. It was very hard to pin point, and I went to the smoke and CO alarms I have, but not form them. Again after 20 seconds it stopped.
Back to work even more confused. 15 minutes later it happens again. As I frantically search I notice something glowing out of the corner of my eye. My phone is lit up. Habitually I pick it, and the BWUUUUUM stops mid note.
I finally put it together. My phone is on vibrate for some reason, and apparently I managed to leave it dead center over the cubby portion of my nice solid maple TV cabinet. The damn thing is resonating the vibrations like a Stradivarius, with it’s solid wood box, and port holes in back to direct the sound against the wall and bounce vaguely around the house.
Stupid Vibrate mode freaking me out.