possible idler or tensioner pulley,use a mechanic's stethoscope or a long screwdriver and carefully while the engine is running touch the end of the screwdriver on the pulley center bolt and usually you can tell which bearing is out right away. This is just a guess because I haven't heard it myself and there are alot of moving parts under the hood.
I am having the same problem. Replaced tensioner and all rollers, (found 1 bad roller) also replaced P/S pump (had about 1/4" pulley play). After putting it back together it was very disappointing to find there was no change in the loud whining and tapping noise. However, I did notice that the A/C compressor clutch always stays engaged constantly. Appears this is an A/C compressor and/or clutch issue. Double check your compressor/clutch, make sure it's operating properly. Should disengage when A/C is turned to the off position.