If you try this command ...
ps -aefl | grep pulse
you should see a pulseaudio process running, something like
1 S stevea 17417 1 0 69 -11 - 117715 poll_s Oct02 ? 00:01:43 /usr/bin/pulseaudio --start --log-target=syslog
It *sounds* like that process has died.
You can verify by trying the command *AFTER* the problem occurs. If the pulseaudio process is gone, than that would confirm my suspicion.
There *should* be log messages from pulseaudio in /var/log/messages.
sudo grep pulseaudio /var/log/messages | less
Not a fix, but if you want to restart the pulseaudio service you can do so with ....
or for KDE use,
(use the start-pulse... command as user not root).