"If you hear the startup sound but nothing else, or if some
applications work and others don’t, this is for you. If you
have no sound at all, there is a link at the end of this post for
more extensive troubleshooting help but you should try this first
anyway as it may solve your problem and will not make matters
worse.Make sure that your system is fully updated.
"First you need to get some missing packages with Synaptic.
These packages were not installed by default but are important for
getting your sound working properly:
"This is a little Default Sound Card application for choosing
the default sound card for alsa.