It's certainly loud, but I found this conclusion to be quite interesting.
When the video card is idling at your desktop the fan is near silent, unless you have an open case system or have it right beside your head, you aren't going to hear it. However, once the temperature ramps up the fan moves some air vigorously. There aren't any annoying ramping speeds or varying RPM fan noises, but at full load there is a rush of air you can hear. This is not a silent video card by any means when playing a game for hours on end. This is to be expected for such a beast, two GPUs is going to need some air moved. However it is not annoying albeit heard.
These cards are the fastest around, undoubtedly. But, seems like anyone spending the money for these suckers will be best served water-cooling the beasts.
Honestly, if you can afford $700 for the card, you should well be able to afford the water cooling setup to get these cards going.