[David N.]

A boxster has two fans on the front either side by the radiators. Usually the fan will turn on (or up, I forget) with the A/C, or when the coolant gets hot enough. If you are hearing a new sound where you heard nothing before, I'm guessing perhaps a bearing is going out that's making it louder than it should be.

Usually you can't hear the fans from inside, but you can faintly if yer standing near the nose of the car while they are on. If you are certain it's making sound on only one side tho, then there is definitely something amiss.