So... you definitely DO hear the "crack" sound of the bullet breaking the sound barrier when you are behind the gun, at least when shooting a 22 rimfire RIFLE. With a pistol or with louder cartridges, the sound of the muzzle blast is so much louder that it drowns out the less-loud sound of the bullet breaking the sound barrier, unless you are far enough away from the louder sound of the muzzle blast (like downrange).
Not quite. While working up loads for my 10mm, many years ago, I discovered the supersonic loads were FAR louder than the subsonic. Differences of only 50 fps during transonic testing were substantially louder.