no sound on ubuntu 12.04?

[Yangfizz]

the sound was working just fine yesterday, and for some reason there is no sound today.

[Aramil of Elixia]

probably a speaker error, but 12.04 is full of holes anyway i miss my 11.04 :(

[Athar]

Check that the right sound output device is selected in sound settings.
It sometimes randomly switches to the graphics card, so you won't hear anything when you've disabled sound on your monitor.