Comment 40 for bug 696841

I can confirm this persists in Ubuntu 14.04 and vlc 2.1.4 - after seeking, vlc may or may not play sound afterwards. Sometimes I have to repeatedly seek again and again so that there's sound in the video.

Many thanks to firesock for the workaround. Selecting "ALSA audio output" and "PulseAudio Sound Server" seems to fix the issue. Just make sure to restart vlc after changing the setting, it doesn't seem to be applied until you do.