Thanks guys.
It appears that our wires are running through a conduit, except the VHF which I think is wrapped in pipe insulation. Like I said, it's kind of hard to see in there, so I'll have to figure out a way to get a better look. I know one thing...It started last year, and I think maybe the conduit broke loose when the guys in the yard were moving it around with the sling and boom truck. It drove us crazy at anchor so I HAVE to quiet it down before we launch this year. If it is a loose conduit, I will first try to drill a small hole beside where the conduit runs, then fish a hook in the hole and try to pull the conduit up tight to the mast, drill another hole (this time through the mast and the conduit), and try to pop rivet it. If that doesn't work out, I might either the foam, or, try to stuff noodles, sponges, or something else up the mast.