Does other web-pages give you sound??? (like youtube etc.)
Is it possible to play some sound from your HD (like music, ... with XMMS / Amarok / ...)
Maybe this thread on PCLOS-forum is helpful
firefox no sound
Or try the following:
Probably the problem is that the order of your cards is wrong in the preferences of PCLinuxOS...
Assure yourself that the audio-manager is set to ALSA,
and open a Konsole, do
(type your root-password) and run then
, selecting as primary card your audio-card