Drawing your weapon because of a noise is not smart at all. Unless that noise is a gunshot in the next room over, or some other noise indicating an immediate and close proximity threat that is potentially handleable using a gun (a ceiling collapsing from heavy snow load would not qualify). One, you would endanger others, and two, you would look like a complete idiot.

If I were in a restaurant, heard a loud boom, and then somebody stood up, drew a gun, and shouted "everybody get down!" I'd probably draw my own firearm and shoot the guy thinking he was attempting an armed robbery. I would certainly do my best to determine the guys intent before considering firing my own gun, but my initial thought process would be that he was a significant threat - an armed criminal.