heh... "fan chamber".... sounds like we're talking about a device for testing aerofoil shapes.
What sort of buzzing are you hearing? Does it sound more "electrical" (although I don't think a GPU has any electrical components that buzz, that's more the domain of high voltage steppers like those you see in a television or monitor) or as if there is some sort of physical problem? It could also be that the card bracket isn't screwed on tight enough and this causes reverberations to be making noise.
Congratulations on getting such a low GPU temp. my GPU hovers around 70 degrees, (75 degrees at the moment due to this awfully hot weather we've been getting), and that's after I personally removed the heatsink+cowling assembly and replaced the generic paste on the GPU with some Arctic Silver (I did manage to lower the temperature by a good 5-10 degrees- it used to hover at around 80 and usually crashed when I ran anything that used it more then a smidgen.
There is certainly zero connection between the clock speed of your GPU and the buzzing sound you are receiving, but if you are ever curious, or have issues that you think a downclock might help diagnose, you can use a tool called "RivaTuner" to perform this task.
Anyway, my stance here is that the problem is clearly physical- the chips themselves don't have any mechanical operation that can cause a buzzing sound, and usually capacitors will make a "squealing" noise, if at all (and usually only when they are about to burst), which leaves, of course, the fan itself. It could be something as simple as a loose fan or some other small component was moved by your cleaning efforts and is now "caught" in the fan blades- a sticker or other small flexible material.
Barring the obvious physical obstacles, it could be that if you cleaned the GPU and blew on the fan with, say, compressed air, you could have damaged the bearings by causing it the rotate backwards from it's intended direction. I've never seen this happen but I doubt it's impossible.
Replacing a GPU fan, in my experience, is sort of annoying. In my case, I had a 5500FX that suddenly started to have "extended "hangs" while playing games. Why it was one of my first threads here ever, long before everybody gave up trying to get rid of me
(
Link. It turned out that while underclocking the card solved that problem, the root cause was that the fan was completely busted. Perhaps due to fate, I had a altogether useless PCI Nvidia 6200FX sitting around, so I just grabbed the fan from that and threw it on the 5500FX and it still works happy as a clam.
of course if you don't have a jungle of spare parts lying around, I'm sure a local repair shop has one, and they will probably be able to supply you with a compatible GPU fan, as Patio suggested.
