I was really sick of my Torando and my Delta fans, both pushing almost 60dB, Both are still very loud even running at 5V. I then figured out that most of the noise is from vibration, so removing the fan-guards helped, but it was still very loud, so I got some foam, and some epoxy, glued foams on all 4 sides of the 2 fans, now to my best estimate it's about 30% quieter than before at 5V. On full blast, it eliminated the rattling noise, but the high-pitched whine sound is still there. For all you loud fans owner out there, try this, it really helps.
-Intel PIV 2.6C @ 3.276G -Asus P4P800 -OCZ Copper 2x256 4000EL memory @ 252mhz 2.5-3-4-6 -XFX 5900 128meg 450/900 -SB audigy -120G Maxtor Diamond Plus9 S-ATA150 hdd -450 Enermax PSU
-Intel PIV 2.6C @ 3.276G -Asus P4P800 -OCZ Copper 2x256 4000EL memory @ 252mhz 2.5-3-4-6 -XFX 5900 128meg 450/900 -SB audigy -120G Maxtor Diamond Plus9 S-ATA150 hdd -450 Enermax PSU