When I upgraded from Ubuntu precise to quantal, I lost sound, wifi, X res above 1024x768, and ethernet. I updated several times, and wifi and internet came back. I upgraded to raring. Still no sound.
I looked at about a hundred threads on pulseaudio, alsa, Dummy Output, no sound.
When pulseaudio has only Dummy Output, you probably have other devices but something has taken them over before you got pulseaudio loaded.
sudo fuser -uv /dev/snd/* /dev/snd/by-path/*
ls -l /dev/snd /dev/snd/by-path
...revealed that I had "roard" (roaraudio server) owning my speakers and headphone jack. dpkg --list '*roar*' and dpkg -r roaraudio and all of its deps, done. I did then do this but with roard gone I don't think it's needed:
sudo killall pulseaudio
sudo killall -9 pulseaudio
rm -rf ~/.pulse*
sudo rm -rf /tmp/pulse*
Another thing that can take over /dev/snd devices is Login sounds. Websearch on that, different things to do, mainly a gnome and/or Ubuntu issue. The most devious problem was some microsoft sapper hid the Ubuntu quantal and raring login option for Gnome login sound in startup apps.
gksudo gedit /usr/share/gnome/autostart/libcanberra-login-sound.desktop
...and edit or add a line "NoDisplay=false", without the quotes. Default is to hide the option to disable login sounds, even without NoDisplay=true!!! Unbelievable microsoft sapper!!! Did Paula Broadwell email a threat to his wife, or what?!! Bribe or threat!?! Enquiring minds want to know, since transparency with accountability has FAILED. Devious.
Then you can disable login sounds: