This thread has proved most useful in my hour of need!
Having a Zoom conference in Wednesday night I had no sound on my Dell XP15, recently updated. I had to fall back on dual-booting into Win 10 to join, which did not please me!
Now with the advice about pavucontrol everything works as it should, so many thanks all!
However, (running with Mate) the Sound set-up does not play any sound at all, nor recognise the microphone. Has anyone any idea why this should be so, or should I just be grateful that the microphone and speakers work?
(on an off-topic note why does MSCrap tell me my computer has a fault and it will restart, when it is clearly the bloody software that's faulty?)