I also checked that the file ~/.local/share/Steam/SteamApps/common/Portal 2/bin/libMiles.so has the correct case. The volume meter in pavucontrol for that stream does not show any activity either. Nevertheless, I disabled all other unused audio devices, just to be sure, but that did not change anything. I do see an output stream called 'Portal 2 : Simple DirectMedia Layer' both in KMix and pavucontrol, and it is assigned to the correct audio device and it is not muted. I already checked and excluded these issues from the similar bug report #60: Mixer Settings The game runs fine otherwise, I could complete several levels in Chapter 3 without any problems (after installing the closed nVidia driver). Portal2 was just installed a few days ago (March 2014). I am on openSUSE 13.1, 64bit, PulseAudio. Other Steam games on my Linux laptop have sound without problems. I do not hear any kind of sound with Portal2.