How many hard drives have you had to compare it to? I've had 11 seagate drives in total, and none were obnoxiously loud, but they certainly weren't silent.
I never really knew the difference until I tried my Hitachi Deskstar, it's virtually silent.
As for the 7200.11 being fast, there are many cases where the 7200.10 outperforms it...don't get me wrong, it's still an awesome drive...but it's nothing amazing and if what he wants is speed and silence I don't think I'd recommend a seagate.