Hey mate. From having a search around, I discovered it is a common problem, and if you wish to replace the fan, its part number is BSB0705HC, -8Z02 apparently, but you can't obtain it through Logitech and need to obtain it via 3rd part. If want to try fixing it first, you can try removing the fan, dismantling it and cleaning any dust/debris from inside of it. Also clean any ducting and the heat sink its self as normally, nosy fans are due to being over dusty or over worked.
Also, this link contains a bit more information; http://forums.logitech.com/t5/Revue-and-...
Hope this was of some help
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