Often enough, you don’t measure how important something was until it’s not there anymore; case in point with the radio chatter in FEAR2 (as I have just started playing it, I won’t pass any judgment on the game itself at this point).

In the original FEAR, you could hear the enemies’ radio chatter. This had several uses:

• They provided information regarding the opposition you were facing: when a squad had been decimated, the comm chatter of the survivors would tell you just that: “No way!”, “I got 2 men down!”, “I need reinforcements!”
• They increased tension: “Flank him”, “I have him in my sights”

The last one I realized while playing to FEAR2:

• They signaled someone’s presence in the area: what keeps happening to me in FEAR 2 is, I’d kill everyone in a room, then start looking around for some ammo or intel… and I’d get shot at point-blank by an unsuspected enemy that was sitting right next door; as this would never happen in the real world – the noise of a heavily armed soldier moving around would be enough to reveal his presence -  I found it a bit frustrating.

And in my understanding, it really fit the philosophy of the first game: it’s not about straight up surprise, but about the anticipation build-up: paranormal activities were always “announced” through cracking static in the headset, and replica soldiers attacking where similarly “announced” through these audio cues.

Some other noises would go in the same section: an elevator beeping when stopping on your floor or a door slamming open would suggest an imminent assault, whereas most of the time in FEAR2, the player would be the first one to get shot if he had not seen the enemy (and they can see you very well).