I believe I am responding to the person with the acer aspire with a nvidia card in it running 9.04. This worked for some folks over at ubuntuforums.org. I think they had Realtek cards.
The following may work anyway, and can be undone by merely opening the file again and deleting the lines added if not. They are easily found due to being at the end.
Reboot after each change to /etc/modprobe.d/alsa-base.conf
Run the following command in Terminal
sudo gedit /etc/modprobe.d/alsa-base.conf
Add these 2 lines to the end of the alsa-base.conf file:
alias snd-card-0 snd-hda-intel
options snd-hda-intel model=auto
If those alsa-base.conf options don't work:
alias snd-card-0 snd-hda-intel
options snd-hda-intel model=acer-aspi
On my sony vaio I needed the last line to be
options snd-hda-intel model=sony-assamd
Unsolved 
