User verstrix just showed me the same errors as we see in this forums post: https://forums.funtoo.org/topic/4805-cant-get-sound-to-work-solved/

The solution in the forums post worked for him as well.  Basically:

emerge media-libs/alsa-lib consolekit

rc-update add consolekit default

/etc/init.d/consolekit start

at which point `pulseaudio` and `pavucontrol` should both work as expected