Thanks for the question Brit! :P
That investigation was more or less impromptu, and involved myself and Jared, our tech manager. We didn't have a full set of equipment like normal, just my Sony Digital Cam and a Sony Digital audio recorder. Nothing came through on the pictures, but we got that weird voice on audio. It only happened once, and only after I asked my first provoking question. We were by ourselves in the graveyard, as it was almost dark, and the gates would soon be locked. The entire time we were there (an hour and a half or so), only two cars passed by (only one side is bordered by a street - Church St which is one way - and it was quite chilly for anyone to be walking about).
I don't usually provoke potential spirits, but I thought just maybe I'll get a response. John C Calhoun was staunchly supportive of southern rights, but died a little over 10 years before the civil war. Thus, asking if he knew the south had lost the war just might make him a bit angry.
It's still hard to grasp that someone dead for 158 years might be able to communicate, but there's a voice there, and it was awesome when we first heard it.