Silent, unmarked arrowshaped aircraft flying low over the University at Buffalo. Was it an experiment?

I had all but forgotten about it until one evening when I saw a woman on a UFO special.  She described a ship and showed a rough sketch of it.  It shocked me!  I got excited and began to jump around the room shouting, "That's mine! That's mine! I saw that!"  My companion didn't know what to think of me and was quite incredulous.
September, 1971 I was two months from my twentieth birthday.  I was in the habit of taking rather long walks, especially on mild and pretty autumn days as this one was.  I found myself walking along Main Street in Buffalo, in front of the State University of New York at Buffalo.  In those days, there was not yet a northern campus.  I was walking north on Main Street, nearing the front of Hayes Hall.  The sight of it is remeniscent of days when a stately appearance inspired respect in the viewer.  I was busy thinking to myself that there was no one anywhere to be seen.  A thing came flying west over Hayes Hall at a very low altitude, from the direction of Bailey Avenue on the opposite side of the campus.  What was it doing there?  This was not the airspace I would normally see aircraft use.  Was this an experiment of the University?  Was this a military experiment?  This was Sunday.  Niagara Falls was the direction the craft was flying, but why was it so low and who could be flying it?  There were no windows.  As I watched this thing in wonder, I was greatly surprised that there was NO SOUND!  This thing was just above the trees and there was absolutely no sound.  I saw a heat signature at the back of the craft, that somehow gave me a kind of reassurance that I might be watching something I could relate to ; something within my experience.  But there was no Sound.  None.  There was no audible competion on the street.  No traffic. No people.  Just me watching that thing fly fly low over the University, the trees, me, the street and the houses.  It flew directly over me.  It was shaped like an arrowhead without a stem.  It's color was green, like an Army jeep; a new, clean one.  This was why I thought it might have been a military experiment.  But it had no markings on it.  Not on its side, not on its bottom.  Just the green of a new jeep.  And no sound.  I got so freaked out I still don't remember how I got home that day.  I know it didn't take me long, even though I residence at that time was five to six ! miles aw ay on the corner of Eagle and Madison.  I was so excited relating this sighting to my mother that she had a rough time trying to calm me down.  It was a very disturbing experience.  It is still disturbing repeating it here.  This was my second sighting.
Time and date are approximate.  PD