There are no supersonic speeds unless the game is abused. Above 40-50k the atmosphere doesn't work right (a flaw in the model) and do you really think you could fly a WW2 design up into the outer edges of space itself (70-90k) as is done when making these "mach 1 breaking" attempts in-game?
No WW2 design could break the speed of sound, and any that do in this game is just a flaw in the game itself, and usually under gamey conditions or offline screwing with the wind.
So, no. No sonic boom, because none of these planes can go supersonic.