If you have experienced no sound problem for VLC player on Fedora 11 under VirtualBox, you can try the following steps.
- Click on Tools -> Preferences.
- Click on Audio on the left.
- Under Output section, change the Type to ALSA audio output.
- Close VLC player and invoke it again.
If the sound is still not working, try to select other types of auido output and see if it works.