Ok, this lies outside my area of expertise. I'm sure someone here can answer this question. When an aircraft breaks the sound barrier, is there only one sonic boom, or does it travel with the aircraft, creating many sonic booms. I believe there is only one, but I heard somewhere, perhaps on here, that there are many, and that is why the Concorde is not allowed to fly over land at supersonic speeds. Also, is there a sound when the aircraft returns to subsonic speeds? Thanks in advance.