Passing on this information in case it may be useful to others.
Some months ago I posted a message about my sound on CentOS 6.8 no longer working. I'd done considerable research on the net and found no useful information on the cause. The sound worked if I booted from a live DVD of CentOS 6.8, but not when I booted from the hard drive.
Recently during a system update that included a new kernel there where some very interesting messages from yum about the problem but no information that helped with a solution. Someone else recently posted a message with the same output from yum. None of the suggestions helped with my computer though.
Then, just on a whim, I logged in as root and the sound worked, but only if I logged in as root.
Long story short: Copying the files in /root/.pulse to my home .pulse directory solved the problem. I now have sound! I have no idea how those files in ~/.pulse got changed. It would be interesting to know if anyone has any ideas. (And, no, I did not do any messing around with system configuration by any means, so that's not how the files got changed.)
Jeff