Dinging Dump Trucks?

All while I was driving on the causeway today, I heard a bell. It didn't fade into the distance like it would've had I passed it. It was too high pitched to be ringing loudly from a great distance. I was in the middle of a salt marsh, which does not contain anything that rings. It sounded like it was attached to my car, but wasn't coming from anywhere inside, because I could dim it down by rolling up my window. There were no obvious bells attached to the dump truck in front of me.

So I spent the entire drive thinking, "what the frell is that??"

Then I got on the island and to the intersection with the gated community. The dump truck in front of me turned right, and I turned left. No more bell.