If you're using Linux Mint 13 with Cinnamon and don't hear any sound, it means the speker of your graphics card and the onboard sound card conflicts. To overcome this, open Settings->Sound dialog (or via sound icon on the taskbar).
Move to the Hardware tab. Choose (click on) GF108 item and look at the Profile dropdown menu at the bottom. Choose "Off " in that menu. Now you should be hearing some sound!