Titanium too!
I know my 15" Titanium does that as well. it's really not that loud, but if the only noise you hear is your fan on the PB, then it gets annoying. It sound like a squeaking noise right? That's what I'm hearing. The funny thing is that it only makes the noise while running Safari (either navigating to a page or loading something). I've moved to Mozilla. I don't like Safari (don't kill me please) mainly because it doesn't work with all the pages I go to most often and I don't like switching between browsers. Mozilla's awesome. As far as the sound...I dunno. Our Mac technician said to try installing it under a new user profile, but that didn't do jack. I don't know what to tell ya. 😕