I think the Blacks are quieter than they used to be. I have one that is coming up on three years old that is one of the noisiest drives I've ever owned (although it's never had an problems in operation). OTOH, the ones I've bought over the last year have been pretty quiet. They work well in RAID-1 pairs too.
My Black drive in my other build which is coming up on a year and a half now, has been pretty quiet under load.