Volume can be controlled through several panels. Which might make this problem of yours tricky. I will list both the "obvious" ones and the lesser obvious ones. Go through this list, and hopefully it will fix your issue.

1. You may have a physical volume controller on your headset/speaker which is turned down (or set to not accept 5.1 dolby digital sound). Try toggling with this/these controllers.

2. You may have turned down the volume (in general in windows). There's an icon in the system tray which is portrayed as a "megafon"). Make sure this is not muted and it is at a proper level.

3. Even if your volume is not muted in the system tray, you should click on it and you will see the link "Mixer". Click on this to see all current software running. Age of Conan should be listed there, IF you are running the game while checking the "Mixer". It will NOT appear if you have quit the game. Check if this is muted or lowered to minimum.

4. In game, go the sound settings and set everything to default by clicking on the "Default" button.

5. If neither of these options help, you might have a corrupt "Age of Conan" installation, or driver issues concerning this game. In either case, reinstalling driver(s) and/or game might help :-)

Good luck!