Mystery noise...need troubleshooting help

Bert has developed what I can only describe as a "cyclic ringing" noise while driving. It is a moderately pitched rotating solid on sheet metal kind of noise. I thought perhaps the stupid stamped metal brake backplates on the rear were rubbing, but they aren't. Brakes aren't dragging or down to the squealers (though this sounds different than that). The diffs and trans aren't the source. I'm stumped. Cannot find the source. Suggestions?

At all RPMs ? Any difference in speed ?
I once had a similar " noise " could not locate until I crawled under with it running in gear( with someone I trusted in the drivers seat )
it was a small piece of rock wedged up in near the left side cat , just did it driving, not idling, or revving it up

Rear CV on the front driveshaft? Mine had a similar noise and it was that. It sounded like if you rub your finger around the rim on an empty glass. Then it turned into a chain dragging noise as the joint got worse and worse.

Mine was the front bearings. Swapped out the front ABS hubs and had blissful silence again (and it got rid of the ABS caution light on the dash).

In my experience, noisey front wheel bearings sound like mud tire growl coming from the front end. They had no play so I thought it was something else, gave up and took it for diagnosis. He drove it, jacked it up, turned the front wheels and listened with a stethescope and said it was the front wheel bearings starting to roar.

So if it is not a mud tire growl or roar, I would get it up on jackstands, check the driveshafts, etc, and look around for any foreign debris lodged anywhere.

I'm betting on a rock somewhere, or driveshaft joint.