I recently installed Fedora 16 (KDE spin) after leaving a many-year Mandriva relationship. I had no sound immediately after installation. Since I had saved the home filesystem from Mandriva, I thought that was the problem, so I reinstalled completely clean.
Unfortunately, I still experienced the no-sound problem, so I dug around. What I eventually found was that my computer had 2 sound cards, and Fedora/KDE was applying the one to which no speakers were connected. (I added a SoundBlaster a few years ago since the built-in card was not working correctly).
However, in doing so, Fedora/KDE completely disregarded the existence of the good SoundBlaster card.
Where I eventually made the change that worked was to go into
System Settings | Multimedia | Phonon | Device Preferences | Audio Playback then select each sub-member within the tree. Click on SoundBlaster card; click Test button; click Prefer to move to top (and apparently enable this card over the built-in sound). I also did this for each sub-member under the Audio Recording tree.
Then click Apply at the bottom of the screen.
Hope this might help somebody else.