Call of Duty Black ops no sound

You can try the following steps:

1. First of all start the game.
2. Press alt + tab.
3. Open the system try by your clock and position the icon which looks like a speaker.
4. Right click on that and chose “open volume mixer”.
5. This will open the Call of Duty: Black Ops volume control. Drag the slider to top.

Guys???

What happened, i did facing the same thing. Very2x dissapointed