Interestingly, it has ceased to work again. I have to rm -r ~/.config/pulse and either log out and back in or reboot for alsa to work. The question is how to make it persistent.
I’m not sure what the issue is. Hardware stuff can be complicated. I’m not Gnome user. It could be an issue with polkit as described here? I’m not that familiar with Gnome and Polkit.
Check out the whole page for Pulse Audio issues. There is also an alsa but i think the issue is the pulse audio as that is what is listed?
I have one machine through HDMI and another one through DP connected to the same display. On these machines Folding At Home Installation Procedure runs occasionally. I guess that this is causing the problem.
Any ideas wrt restarting a service or similar after rm -r ~/.config/pulse to avoid having to log out and back in? Thanks.
How is your sound hooked up. To separate speakers or through HDMI cable to speakers in the monitor or out to tv. Have you tried identifying what sound device is running.
To start pulse audio
pulseaudio --start
OK. The sound travels through HDMI / Display Port to bult-in speakers of the monitor and if all works well ( ~/.config/pulse removed and log out/in) that is also shown in Gnome Settings and works.
Interestingly, if pulseaudio --start is then run, we are back to “Dummy Output” being displayed in Gnome Settings and audio is not working.
I should further mention that sudo alsamixer shows Nvidia i.e. HDMI / DP running whereas alsamixer shows pulseaudio running (now).
Both Ubuntu and Fedora do not have an issue on that desktop.
Have you tried it without using Display port? Two different cables …two different technologies … i think it’s confused. 
Very likely. I am still looking for a way to avoid having to log in and out again after deleting the config file. How to regenerate it?
You may be able to set the default sound device. This stuff is kind of complicated because there is so much to it. Look at 3.1.3.1 here: Not sure if that’s the answer or it may be simpler by editing some other configuration files such as (/etc/asound.conf)
Example:
pcm.!default {
type plug
slave.pcm {
@func getenv
vars [ ALSAPCM ]
default “hw:Audigy2”
}
}
I think you are just going to have to do a lot of reading on Alsa and Pulse and try to figure it out. Alsa and Pulse are both used so like i say this is tricky stuff.
https://wiki.archlinux.org/index.php/Advanced_Linux_Sound_Architecture
Much appreciate the this very useful wrap-up of how to tacke the problem!
I think, I have fixed my problem, though, by activating “HD Audio” in the BIOS 
Well that makes sense too if it’s turned off in the Bios.
Hope it’s working for you now.
Yes, it is working fine. I also noticed an update of the alsa libs.