With respect to everyone I simply wanna say that, this is not a problem related to sound card or any hardware devices. I faced the same problem. I installed the game in my PC where Windows 8 Pro 64 Has been installed and did not get any sound once the cut scene of the opening ends. From there no sound at all I found. I probably did everything what every other websites and individuals suggested but not a single one worked. So to solve the sound issue the only thing that you have to do to replace the game with a new one. Another probable solution is to install the suitable directX for Far Cry 3 and many of my friends said it worked for them. Also the save game option will solve upon replacing the DVD. Do not forget to install other opponents/resources (Dot Net Framework, VcRedist, Ubisoft Launcher and so on) came with the DVD. So thanks everyone.
With Best regards,