For what it's worth...
having gone through, um, four or five different laptops the past four years due to theft, manhandling and various incompatibilities, I can say that my current model, the Acer Travelmate 292LCi, featuring a 1.5 Centrino, is an amazingly quiet laptop, and this is under full load.
I use it for making music. It's actually so quiet I don't have a problem using it for recording in the same room.
Don't think they make it anymore, though.
I previously had an Acer with an AMD athlon-mobile, which was far far too noisy for comfort.