A quick and easy way to check the dust cover is to push in on it slightly in a couple of different places while the engine is running.
If that's what the sound is coming from it'll change drastically when you push in on it a little. (by the starter, down at the bottom and up on the passenger side)
I like to use a hammer handle or the like instead of my hands in case a bolt catches an edge of the inspection opening or up close to the block somewhere.
That sounds like either loose flex plate to crank bolts or the converter to me.
I would have to pull the pan and make sure the converter isn't dumping metal in it, because it'll trash that trans pump right now.
