In a perfect world, option 1 with a variation. Delay for a second as I reach for my EDC bag, then hit the floor and make sure my people were with me down there if there is anything that in the first second or so doesn't look that 100% normal. Then begin sizing up information.

However, I've spent most of my life under or near military flight lines- sonic booms are sonic booms. I have hit the deck for other explosiony-noises, but there were two recently returned Gaurdsmen in the room the last time. We all got silly looks, and they looked at me like "who are you, you don't look like one of us". (Big belly, long hair, working on a ZZ Top beard. I don't look deployable as anything other than a paperweight. Or a really, really cranky budda.)

EDIT: LOL @ Susan.