Rotational scraping noise from front end

[$chlitz]

i've got a new noise coming from my front end, and i'm pretty sure it started two weeks ago after i had my wheels off. it is NOT the brakes--the noise comes and goes, speeds up/slows down with the vehicle, applying the brakes has no effect, steering/turning has no effect. it sounds like a light metal on metal scraping to me. i was reading up on replacing a torn CV boot and it seems that there is some kind of "dust bowl" on the hub that can come loose and then either needs to be tack welded back into place or just cut off and removed. my front wheels were VERY VERY stubborn to come off, so i was pounding around on the backside of the wheel with a rubber mallet quite a bit. possible i whacked this "dust bowl" and knocked it loose?

i guess i'll pull the wheels off again this weekend and see if i can track down the noise. just hoping someone might be able to chime in and let me know what else might be causing a noise like this so i can check all possibilities. thanks!

(i realize this is difficult to diagnose without actually hearing it, but just looking for possible causes.)