Aside from the occasional gunshots in the distance, grenade explosions, and little 'ting's from the spade, Ace of Spades isn't exactly filled with sound.
Especially when you're just walking, the sound of your footsteps perhaps, but nothing else.
Nothing is there to be heard, and it gets boring, and frankly, your immersion may be broken.
But I want to suggest implementing environmental noises, all around you, birds tweeting, leaves rustling, wind whistling, the works.
Imagine this scenario:
You and your squad is patrolling a plain. There are trees to the west, more plains to the east.
You and your squad walk slowly, hoping to pick up the faintest of distinct noises from the enemy.
You hear the birds in the trees chirping, ever so faintly, the trees they are perched in are rustling softly in the breeze.
For a split second, you are at peace, your mind out of the battlefield.
The birds chirping, leaves rustling, wind blowing, all drained out by the sound of the distinct 'tik tik tik' of a landed grenade.
Then, boom, an explosion, and you and your squad are yet again immersed in warfare.
See? That adds a lot more drama. This scenario may not be likely to happen in the actual game, but ambience may still add some drama and immersion to your gameplay.
I think servers should choose the kind of ambience for their servers, based on what flavor map it is, be it forest, tundra, desert, mountains, city, etc.
Environmental sounds should vary from birds chirping, wind blowing, leaves rustling, sand shifting, crickets, frogs, various other animals, waves crashing along the sea shore, underwater immersion (all sounds muffled while underwater), and much more.
You may be thinking ambience is pointless, but I think it adds immersion (Yes, I know I keep saying it, but I can't quite find any other words), like I said before, and it gives us a thing to do, you know? Listen to the environment.
Yeah I may seem like a hippy by now.
But Mat^2 please consider this. I'm suprised it has not been added yet.