I'm running Linux E6520 3.2.0-56-generic #86-Ubuntu SMP Wed Oct 23 09:20:45 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux on a Dell Latitude E6530. (This is a new machine; have run the same version of linux on an older machine for a year, without this happening.) I've been losing sound regularly, though have not been able to isolate the trigger for this.

I've scoured the web on this subject, in particular

https://help.ubuntu.com/community/SoundTroubleshootingProcedure

and

Audio stopped working suddenly in 12.04

Nothing from the first site seemed to work for me. From the second site, I learned enough to be able to fix the problem when it happens, but nothing on the web has helped me figure out why the problem is happening in the first place.

Patching together stuff from the web, and with some blind luck, I've found that the following steps seem to restore sound

pulseaudio --kill
pulseaudio --start
pavucontrol -> output devices
         Click on the "Mute audio" icon, which mutes audio
         Click on the "Mute audio" icon, which unmutes audio.

This obviously doesn't make sense: audio wasn't muted in the first place, but somehow, magically, toggling mute audio off and on seems to reset something.

Can anybody suggest from this information why sound would be disappearing in the first place (it seems as though something is getting muted at the system level, but I don't know what)? a simpler (command-line/script) way of restoring sound, in particular, is it possible to reset pavucontrol from the commandline?

Some other pieces of information that may be of use: The problem is clearly happening at the system level, since I've set up a clean new user, and this user has the same problems that I do. So user fixes like deleting the .pulse directory aren't (and don't) help.
Sound works fine in Windows (dual-boot) so it's not a hardware problem

Any help/suggestions on this would be most appreciated.