Hey I did this last night! It WORKED! It is extremely simple to do. Find or buy a spare Molex connector (the ones used on your power supply with 4 leads arranged as follows:
1.Yellow: 12V
2.Black: GND
3.Black: GND
4.Red: 5V
The connector on the IHC-H71 is normally connected to 1 and 2 above (i.e. 12V and GND). All you have to do is pull out the GND wire (number 2) and put the 5V (number 4) in its place. This produces a voltage difference of 12V-(+5V)= +7V. This translates to ~42% less power to the fan which I'm guessing produces around 2500-3000 rpms. I can't give you the exact rpms because the fan-speed monitor will not work with this modifcation. My guess is it the fan speed's voltage output is normally between +5V and GND. Well now the GND plane for the fan is at +5V so it won't work.
Temperature wise, I noticed VERY little increase in temperature. However, I haven't tried running the CPU under full load either. My guess is this modification will have a slightly larger impact under load. The heatsink on the IHC-H71 is awesome, and pretty much takes care of most of the heat. If your losing your insanity over the noise issue like me, it is worth doing this quick 5 minute modification.
Just a note on how to switch the leads. There's two tabs that prevent the stub from being pulled out of the connector. I resorted to brute force and pulled it out, and then I repaired the bent stubs by just straightening them out. I then reinserted the stub. A better approach is to use a really fine set of tweezers or something to depress the stop-tabs before yanking the stub out.
Let me know if you need more details. One more thing, I read somewhere that "your power supply needs to be able to handle the extra load on the +5V rail". My Antec480W ps doesn't seem to care...
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