no weapen sound in CF

hi, sometimes i've a problem in CF: i don't hear the sound of my gun fire, and also not the sound of other persons gunfire.

i hear the music in the lobby, but when i play a game, i can't hear the sound of my bullets.
i hear the voice wel. voice like "fire in the hole", "grenade", "headshot" and more.

sometimes there is no problem and i hear al the sounds, but sometimes i dont.
when i try to restart te game sometimes the problem is solved. but most it isn't.

- my notebook is not the problem, the sound is good-

i think it is a bug , i think the problem is my notebook configuration + crossfire, but sometimes there is no problem.

i've tried:
reinstallation
restart
reboot my notebook

who know how to solve this problem?

sorry for my bad english (i'm dutch)