If you hear an enemy fighter before you detect it visually or with your sensors, don't worry, it's just the sound of your fighter escort to the elysian fields, because you're already dead. :smilewink:
But seriously, the sound in lockon isn't so much surround sound, as much as it is a fixed set of sounds for a given camera position. Try panning around your aircraft in an external view while you're flying and you'll see what I mean. You'll hear no engine noise in one position, and then you'll move the camera a few inches in another direction and hear the full roar.