Loud music, combat or industrial noise, fog and areas of glaring light interspersed with pitch dark.. -Makes the game more challenging.
That depends on what you consider a challenge.
If you consider chaos a challenge (it certainly is), then yes, that would be a challenge.
If you think it requires anything more than an itchy trigger finger and pounding three rockstars before each match to be successful... i'd recommend thinking a little harder about that.
Just remember, it's also a challenge to sneak up on people when it's absolutely quiet, or to communicate when it's super quiet is also difficult (I know, it's just as hard when it's loud, for the opposite reason).
Employing a slow/unsteady amount of gunfire/explosion/warzone sound effects has a similar effect of distracting, without taking away the need for stealth.
Interesting game types are super abundant in CQB arenas. If I wanted to have fog, random bright lights and a lot of dark places, and loud techno music, i'd go play laser tag. That's what I'm getting at here...