Hmm I'm not sure why that would be dude... you should be able to hear other's mics if they're using them (and are on your team), unless they've set it up so you can't or something.
I was brand new to online gaming when I got my PS3... I'd also never really played a proper shooter game, so I was pretty terrible back then. Obviously you eventually get better though. Just try not to take it too seriously and have fun!
I was hooked on The Last of Us multiplayer, but now Destiny has taken over... then it'll no doubt be the new CoD I get addicted to.
Anyway, enjoy buddy! May see you around and have a game or two with you sometime.