Growling in Mifflin County, Pennsylvania

I was out in the spring of the year scouting around for turkeys on the southern side of Jacks Mountain near the small village of Ellen Chapel (close to Lewistown). I heard a type of clucking sound in a thick, brushy area and walked closer to investigate. The clucking sound caught my attention because it sounded kind of like a turkey. What was odd, however, was that a turkey would let me approach that closely. As I got closer to the clucking sound, I heard a very low, gutteral growl coming from the brush. I couldn't see anything. This growl really surprised and scared me. I began walking away, but then curiosity got the better of me and I approached the area slowly again. Once again, as I got closer, the low growl occurred. Black bears are commonly seen around this area, but I can't imagine that a black bear would simply hold still that close to a human and growl. Whatever was growling at me was very well concealed because I couldn't see a thing. So after hearing this growl two or three times, I got freaked out and left. The only other explanation I can think of--and the one I've held to for the last 25 years--is that there was another turkey hunter out in the woods, well camoflauged, who was messing with me. I've never told anyone about this incident. I started reading accounts here of people being growled at from thick brush and thought my experience might be of the same nature.