Lastly the noise levels. We measured the amount of noise produced at a distance of 10 cm with at about 100W. 30 dB(A) is the lowest we are able to measure, and values in this vicinity mean that a PSU is inaudibly silent. Everything below 35 dB(A) is extremely silent, and above this level you will start to hear the power supply. At 40 dB(A) and higher the PSU is clearly audible.
The Seasonic Platinum Series 400W is passive so it's obviously completely quiet. The Be Quiet! Pure Power L7 300W, Nexus Value 430W and Huntkey Jumper 400 did not work properly in this test for some reason.
In the top 5 the four Be Quiet! power supplies can be found, staying true to its brand name. The Straight Power E9 450W was so quiet we almost couldn't measure it at 18 dB(A). None of the PSUs in this test were very loud, apparently that's no longer an issue in this segment either. Four models did exceed 40 dB(A): the Huntkey Jumper 300G, the Enermax Naxn 450W and the Huntkey CP models.