I've never ever had a rattle they're simply not allowed, but this just popped up last Sunday.
It's at the rear, it sounds like a whole lot of cable outers banging against the frame.
I gave it a once over, I couldn't replicate it by bouncing the bike! Everything was tight except the cassette, that had movement. I removed it thinking the freehub would have play, but it didn't.
All cleaned an reassembled and it still does it.
I also need to replace the cassette and chain anyway, but I've never had this.
Is there anything you can think of? plus these are the only sealed bearing road wheels I've owned, is rattle a characteristic of these?