Just in case you want a trip down memory lane (and/or in case things regress to where I have to try to beat my head against the wall), I have saved my notes on my prior frustrations with linux sound.
So, the first thing is to find the mixer. No luck in the Applications Menu, and then I ran around in circles trying to install additional packages. This was unnecessary, because xfce4-mixer was already installed. The xfce "application finder" was able to locate it for me among the mutimedia applications (maybe it is in the application menu somewhere, but it will take a better man than me to locate it). And it turns out that at the extreme upper right corner of my desktop is a tiny icon that if you look really close at it and squint just might be a speaker. And it is! Clicking on this gets you the xfce-mixer, and to make a long story short, what made sound work was to change the sound card selection from the original setting of "HDA NVidia (Alsa mixer)" to "Playback: Internal Audio Analog Stereo (PulseAudio Mixer)" then you have to select some controls (select the only choice, namely "Master") and ensure that it is not muted.
And then sound works and life is good.
Adventures in Computing / [email protected]