If i was going to rank my external HDDs (10 being unacceptable):
(fan noise)
10.0 Laci Mini drive
10.0 G-Tech Raid 2TB: <-- Loudest, meant for video editing though
9.5 Drobo (USB model) <-- 3 drive configuration (4th drive is too loud)
(hdd head noise)
2.1 G-Tech Drive 2TB <-- I think it's slightly louder than the WD
2.0 WD Desktop External 1TB
1.0 G-Tech Mobile, WD mobile drives <-- least amount of noise
(and no noise for funnies

)
0.2 Vinyl
0.1 CD
0.0 SSDs/Flash
All is out in the open on a desk...