I ran into this problem recently (but before my upgrade to 14 from 13.2) 
and it took me longer than I want to admit to to discover that it was 
sending all audio output to my VIDEO card.

Try installing and using PulseAudio Volume Control (Ubuntu and possibly 
Debian package name: pavucontrol).

After running it, click on the Configuration tab.  If you see some sort 
of phantom device (such as HDMI Audio if that's not what you're using -- 
my display is DVI and predates HDMI), set its profile to Off.  Next, 
make sure your setting on the Output tab is corresponding to where your 
actual audio is hooked up, such as Analog Output.

Hope this helps!