I was in Gettysburg in March with my sister . We were at Little Round Top looking for our G G Grandfather's PA Reg monument and had my W - 10 Olympus digital recorder. There was a small rock formation right next to the monument. I made a comment about General Burnside as I was leaning into this rock formation. My sister was away for me looking at the beautiful view. The questionable sounds were here.

A few minutes later I looked up a hill and saw a much larger rock formation was above us. My sister wasn't up for climbing the hill so I handed her my camera and went up by myself.. A group of people on a walk way terraced behind this rock formation went past when I 1st got up there. You will hear them. At the point where I got something whe I believe is unexplained ( I was saying in a loud tone how it was wrong to throw trash in a place like this )
I was surrounded on three sides by extremely large boulders and no one was near me.
http://media.putfile.com/Little-Round-Top-clip-2