I have no sound on my imac, with 12.04 from a clean install from CD. I have checked alsamixer and a number of other things. Still no sound.
http://ubuntuforums.org/showthread.php?t=1864114
This is what I did to fix it.
Open terminal
sudo gedit /etc/modprobe.d/modprobe.conf
A new file will be opened, write a line below then save.
options snd_hda_intel model=mb5
Close file
Reboot the computer.
After rebooting, speaker will show in a mute, adjust the sound preference and set "The selected device" to "Analog Stereo Output" or 'Analog Stereo Duplex'"
That was a direct quote from ubuntu forum.
