Turned the computer on this morning and all was well.
Left it on, which I normally do, when I went out for a few hours.
Came back in the afternoon and all audio had disappeared.
Oh, it is Slackware64-current.
pulse has been working very well since it was added to Slackware...
until now.
I've looked at various files, deleted many, and re-booted, but
nothing has worked. The various applicatiions that use sound
haven't complained. It is as if a mute switch has been turned on, but if so, I can't find it.
Any ideas?
Thanks.

You could start by narrowing down the issue.

If these are internal speakers, try jacking external speakers or a headset in the speaker jack and check whether there is sound there. If there is, it's likely a hardware issue with the speakers.

You might also try booting to a live CD of something and testing the sound. If it works with the live CD, then it is likely a Slackware issue.

If these are external speakers and there are no internal speakers, try getting a compatible USB sound card and testing with that.

If you post the make/model of the computer, perhaps there is someone who has experience with that particular box.

I booted over to Xp on another partition and the default realtek audio device wouldn't work, but when playing a video in VLC (for windows, of course) I directed the audio to the HDMI audio devuce on the video card, and the sound came to life. I was able to duplicate this in Slackware64-current and VLC.
I'm starting to wonder if it is possible the realtek audio chip on the motherboard decided to "retire."

The external speakers are attached in two different ways. There is a cable running from the "audio out" on the motherboard to the speakers on the monitor and they are also connected via the HDMI cable running from the video card to the monitor.
As mentioned above, there appears to be no sound coming from the realtek chip to either the speakers or the headphones.

Did you check to see if the realek module is loaded and if 'lspci' sees the audio device? That's the 1st step if you suspect the chip went belly up. Also, There's a '/usr/bin/alsa-info.sh' script that attempts to do some diagnostics.

You can try "aplay" to see what devices ALSA sees, since if ALSA doesn't see the device, then neither will pulseaudio:
Use the pcm device names to figure out where the sound is going:
I had a case once where for some reason, no doubt something silly I did, the sound shifted from REAR to FRONT speakers on an old Soundblaster card (long before pulsaudio was added so I can't blame that). There was nothing plugged in to the FRONT jacks. It took me a day to figure that out until I discovered 'speaker-test'. Nuts.

Here are the two important lines from lspci,


and from aplay -l


and from aplay -L


From speaker test,


It looks in order, but, as frankbell suggested, I just booted from a LiveSlack DVD (dated 2-14-17) and the problem remains. Absolutely no
sound via the default realtek 'AC97 device (aka, NVidia CK804), but you can route sound in VLC through the HDMI audio device on the video card.

I'm no expert (obviously ), but it would appear to be a motherboard/hardware problem. I've been putting off buying a new motherboard until the release of the next LTS kernel, but maybe this will force me to bite the bullet.

OTOH, if it is possible to have pulseaudio force ALL audio through the HDMI card AND to the headphones, then I can live with that, but from what I've read so far while trying to diagnose this problem, that does not appear to be feasible.

Any suggestion would be appreciated.
Many thanks.

OK, I've been digging around in the Arch documentation and found that by setting the analog device as the secondary source I now have sound through the HDMI device on the video card. That adds a new item in pavucontrol entitled,
"Simultaneous output to Built-in Audio, GK20 HDMI/DP Audio Controller Digital Stereo (HDMI 2), Built-in Audio Analog Stereo."

So, sound is now available via the speakers, but I have yet to be able to route it through the headphones.
Work in progress.

Well, no luck with the headphones. It appears the audio ports
on the motherboard are dead.
So, the hunt begins for a new motherboard and CPU.

If it happens all of a sudden, I think there's a good chance that audio chip has gone south. USB with audio ports I think it's kinda cheap. Just saying for alternative, but of course if you got extra cash then a new one is definitely better.

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is this a tower/case or a laptop/netbook

if tower, it might be that your connectors on the motherboard to the audio ports such as to headphones etc are loose and need re-bedding
meaning push down on the connectors.

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Wonders is the MB or the speakers bad cable. Sad if the card is going. had a short on a cable once drove me crazy.

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@cwizardone

To note that I have a motherboard which lost his voice around 5 years ago, then used it in a server box, where do its duty until present.

Losing the audio part is not an End of World, the motherboard can continue to work many years later.

The best option is, in my opinion, to use a cheap PCI audio card, which anyways would outperform the built-in audio.

If you can live with HDMI and headphones, there are plenty of headphones who use directly the USB and appear as an audio device, if you do not want that, a small USB audio stick would do the job.

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I find myself wondering why you even bother with the onboard chip when HDMI works for you. The HDMI should be superior sound and more free of mobo noise so why not just disable the realtek in BIOS/UEFI ? Keep It Simple, right?

Oh, I would agree, but I haven't been able to route the sound to the headphones. The headphone jack orginates on the motherboard and all the audio ports on the motherboard appear to be dead.

One problem I've noticed with using HDMI is the multimedia keys don't work correctly. In Xfce they allow you to mute and lower the sound, but once lowered you can't raise the volume with the key, but have to use the mouse and the slider. Not quick enough. I haven't tried it in KDE-4.

So, you are saying those little eight dollar doogles that plug into a USB port are actually sounds cards and give one a working headphone jack?

Yup, that's idea.

They are some (lame) sound cards, with headphone and microphone jacks.

BUT, they work well, if you ask them for what they're built.

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