My onboard sound card doesn't work; so I use Creative Audigy 2 ZS Notebook with my laptop (Toshiba). I could play sound on Movie Player, but mplayer, real player, firefox (youtube and other flash sound) would not play.
here is what i did to make things work
1) to list sound modules used.
2) Blacklist omboard sound modules in /etc/modprobe.d/blacklist
here is what i did
sudo gedit /etc/modprobe.d/blacklist
#blacklists onboard soundcard. 26th april 2008