Processors and graphics cards can produce a lot of heat, and that heat needs to be transferred away from the hot core as quickly as possible. You'll often see massive active-fan solutions that can indeed get rid of the heat, yet all the fans these days make the PC a noisy son of a gun. Do remember that the test we do is extremely subjective. We bought a certified dBA meter and will measure how many dBA originate from the PC. Why is this subjective, you might ask? Well, there is always noise in the background, coming from the streets, from the HDD, PSU fan, etc., so this is, by a mile or two, an imprecise measurement. You could only achieve an objective measurement in a sound test chamber.
The human auditory system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal across all frequencies. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBA level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement. Frequencies below 1 kHz and above 6 kHz are attenuated, whereas frequencies between 1 kHz and 6 kHz are amplified by the A weighting.
There are a lot of differences in measurements between websites. We measure noise levels in a completely enclosed and sealed-off room. The lowest dBA level that we can measure without any equipment activated is roughly 30 dBA in this room. We measure the noise at 30cm from the side panel.
In idle you can hardly hear the fans. Under wPrime the fans spin at about 1500 rpm, it is not silent but it’s relatively comfortable. The pump was virtually inaudible (even if we cut the fans off) and we don’t have any complaints in this department.