Comment 8 for bug 1786495

I found the fix. It seems funny but it is really fault of nvidia-driver-xxx. It somehow modifies power settings of the system. I am using latest Ubuntu 19.04 with 5.0.0-11-generic kernel but exactly same problem did happen wit any previous Ubuntu version and also with recent versions of Fedora.

I added the following line to /etc/modprobe.d/alsa-base.conf

options snd-hda-intel enable_msi=1 enable=0,1 model=dell-headset-multi power_save=0 power_save_controller=N

# note that pulseaudio -k && sudo alsa force-reload was not sufficient I had to reboot system because the modules were in some wrong state and they did not unload successfully

1. the enable_msi=1 : interupt setting is there because there is no sound after suspend
2. enable=0,1 : I did disabled the intel hdmi, spdif (non PCM) sound cards because some programs just used the diferent card no matter what was selected in ubuntu desktop controls/alsa mixer and this was the most simple method to get it working (you can list your cards by aplay -l)
3. model=dell-headset-multi this is required otherwise you will hear only cracking if you play something
4. power_save=0 without this you will hear nothing or cracking

Note:
You may also need to run sudo apt-get install --reinstall dkms alsa-base pulseaudio to get the system in to initial state if you modified something recently.

Note:
Out of the box ubuntu installation worked just fine, but after reinstall of nvidia-driver-XXX (415->418) / kernel (if the nvidia driver is installed) the sound just stops working and there is no error msg anywhere (dmesg, syslog) and the output is seems to selected properly and the mute etc is set properly in alsamixer.
The problem is that the nvidia drivers somehow modifies the power settings and this breaks the audio.