In the info section of photo below, the photographer states that this USAF B-1B Bomber is making a high speed pass very near the sound barrier. Obviously, if this B-1B did break the sound barrier, the photographer (and everyone else in the neighberhood) would have known it.
My question is: How much faster would this B-1B have to be going to break the sound barrier and create a sonic boom? If it is already causing a shock wave that's forming a cloud of vapour, then wouldn't it be very close? (as in only a few mph short of the speed required).
Photo © Gregg Stansbery