hard to say but could it be the shackles holding the stays to the mast shifting? I hear this occassionally and that is usually what I attribute it to. They can slide a little side to side and I think this is what causes it. I put spacers on and seems to improve.
I second that - it's probably the shackles at the mast hound flopping from side to side. The mast really translates that noise making it sound like it's coming from somewhere else.
I put spacers on all my shackle pins at the hound to keep them centered and from flopping to one side. No more noise.
