I updated from 15.3 to 15.4 and all is well, well :-) mostly.

Sound works when playing video in firefox, when playing musing with mplayer,
etc.

But xbell is no longer to be heard. I miss "vi" baking a beep when I hit escape
at the wrong time. I miss xbiff making a sound when an email arrives (there is
no sound but it still changes the icon to flag-up).

How may we go about debugging missing "system sound" (or whatever it is? 

Just to clarify, I have checked pavucontrol and tried fiddling with all the
sliders. No difference.

Please let me know if I can upload log files that may help.

Thanks,
Ole

Dell Inspiron from 2011ish.