It seems like they got better, but over 20 dB for a harddrive is too much for my liking:
ACOUSTICS

WD Caviar Black 2TB

The first generation 1TB Caviar Black was one of the loudest hard drive we've ever tested, measuring >21/25 dBA@1m (idle/seeking) in our anechoic chamber. While nowhere close to current quiet HDD leaders, the new 2TB version is a huge improvement, generating 5 dBA less when idle, and about 3 dBA less when seeking.
http://www.silentpcreview.com/article1079-page5.html

I wish someone made something like 3300rpm harddrives for pure storage purposes (way overkill for USB 2.0 or most NASes anyway), focused on silence and reliability. All of the drives I have seen that are supposed to focus on reliability are 7200rpm drives, and I bet they are not quiet enough for my liking.