In the past years, users would accept everything just to get more performance. Nowadays, this has changed and users have become more aware of the fan noise and the power consumption of their graphic cards.
In order to properly test the fan noise that a card emits, we use the Bruel & Kjaer 2236 sound level meter (~$4,000) which has the measurement range and accuracy we are looking for.
The tested graphics card was installed in a system that was completely passively cooled. That is, passive PSU, passive CPU cooler, and passive cooling on the motherboard and on a solid state drive.
This setup allows us to eliminate secondary noise sources and test only the video card. To be more compliant with standards like DIN 45635 (we are not claiming to be fully DIN 45635 certified), the measurement was conducted at 100 cm of distance and at 160 cm over the floor. The ambient background noise level in the room was well below 20 dBA for all measurements. Please note that the dBA scale is not linear but logarithmic. 40 dBA is not twice as loud as 20 dBA. A 3 dBA increase results in double the sound pressure. The human hearing perception is a bit different and it is generally accepted that a 10 dBA increase doubles the perceived sound level. The 3D load noise levels were tested with a stressful game, not with Furmark.
Fan noise of the ASUS GTX 660 Ti DC II TOP is outstanding. It is, by far, the quietest GTX 660 Ti reviewed today, especially under load where it is quieter than most other cards. Noise levels are exactly the same as on the famous GTX 670 DC II TOP.