Noise, Please help

I have a 92 prelude with a swapped h22a in it, lately i started noticing a metallic scraping noise coming from the engine bay, and i swear it's a bad bearing or something, weird part is, it only does it at around 3-3.5k rpm and sometimes at around 1500 (when rpms are dropping to idle for neutral). coincidentally its right around the shift points and normal driving rpm.. also it only does it when the engine warms up a good 10 min or so. I just cant seem to find out what it is and it seems to not be as loud when im not driving it (like in neutral just sittin there, and revving it to find it,) its always louder when im driving. Any suggestions would be much appreciated

oh, the engine has around 70k and i just replaced the alternator, thought maybe that could have been bad.. but wouldnt a bad bearing make that noise all the time, even when cold and at all rpms?

Thanks in advance

-Ryan

Maybe your water pump? When mine went bad it made the sound only once in a while. Like a metallic rattling sound.