metal vibration sound as to tin at low idle

Hi,
I have a 1994 ran van b150 3.9 engine. I've always had this sound from the time I bought it. Seems to be getting worse as I'm having other problems. Its at low idle and low throttle--a tinny vibritory sound then disappears as rpms go up. Anyone know what this maybe?

Thanks

One of the baffle welds could've broke loose inside the catalytic converter or muffler, or one of the heat shields on the outside of them.

Get under there with a rubber mallet and start doing some banging around to see if you can narrow it down.

I don't thinks it the catlylectic converter since I had it replaced not long ago. Like said it always was there...
Well I came to realise that Dodge vehicles just don't have it together as far as design in their motors. No mercy on my side for a company thats been beaten by the japs---its about survival today and who makes the best product for the consumer...My surviaval depends on a good running veheicle rather than one that I can't depend on--ya can't beat on dead horses--they don't get up...

Not sure about your 94 but my 86 has heat shields over the exhaust manifolds, One of those may be cracked/loose. Mine also has heat Shields on each side of the engine to reduce heat from the dog box, They are mounted to the floor board. They can be seen when the box is removed.