"my usual rant" goes out to the ones saying that soundcard gives you the same advantage as rapid fire / macros.
I'm not sure anyone is saying that they're the same advantages, but rather that they're both something that wasn't meant to be in the game.
But I agree, you can't compare the 2 in an adequate way.
Like Bart said, having a macro makes you do things in game that you yourself didn't do anything to trigger.
Sound, however, is never triggered by a person themselves (well it's a side effect of actions, but you don't have to press an extra button for it). How a specific sound card processes sound makes it 'good' or 'bad' for exploiting the sound in this game.
Those are both advantages, but they're completely different.
In one you fire faster (or reduce recoil I guess), in the other you hear where the enemy is. You're supposed to hear the enemy close to you (granted not as accurately as some of the cards here allow), but you're not supposed to fire faster than you can move your fingers.