Are you crazy or not? Why are you hearing these creepy voices while picking up archaeology keystones when guildies swear they hear nothing? The resolution, once and for all, found somehow by Jess:
Yep, DBM. Nothing to do with Blizz. The latest update of DBM has an option under general that is called "Make archaeology more interesting". It's apparently defaulted as on, though I would think some of my guildies have updated DBM and theirs obviously weren't turned on.
Here is the DBM change log that details this. Thanks DBM for making me and my guildies question my sanity! Though as Nkm noted, I am still crazy, just not because of this. Hmmm.
I think I'm going to keep it turned on though. It does make archaeology more interesting, and now I'll know where its coming from instead of getting creeped out.