Interesting experience . . .
I was watching TV and they said something to the effect of "the shuttle is coming over Birmingham, Alabama right now . . . " so I ran outside and looked up. Five seconds later I heard two "booms" and I was concerned that something bad had happened.
I came back inside and learned that the shuttle was safe . . . but that when it passes over head it creates "twin sonic booms" that people on the ground can hear. One boom is from the nose, one from the tail.
Pretty strange . . . but I heard it.