There was a bomb developed for the Gulf War (I or II?) which was designed to take the deeply buried bunkers used by the Iraqi high command. It had to go through 50 feet of dirt or gravel then a few feet of reinforced concrete. According to Time Magazine, some wag at the munitions plant even painted the name on it, “The Saddamizer”. It had a time delay fuse, a nose cone that was 25 feet of solid steel and was dropped from 50,000 feet. I wonder if that hit supersonic speeds?
The V1 was a pulse-jet, which apparently are VERY noisy; also called a buzz-bomb. They were subsonic, and the time to panic from what I read was when the noise stopped. What I read was that they ran out of fuel. George Orwell describes setting up lawn chairs on the hill at Hampstead Heath in north London to watch them coming in over London;I thought he said the sound stopped before they dived. You could see them flying in, the noise stopped, then they dived and where they hit a big explosion happened.
The V2’s OTOH, were parabolic flight rockets much faster than sound. When they first began to hit with no warning, the authorities blamed random explosions on gas mains. Some wags started calling the V2’s “flying gas mains”.