In addition to things such as stability and efficiency, there's another factor that can influence your daily usage of the computer: the noise levels. We measure these in a soundproof box at a distance of 10 cm. While this approach does allow us to highlight the differences between models, it also results in somewhat exaggerated findings: 39 dB(A) at 10 cm is barely audible when using your computer at a normal distance, especially when other sound sources, such as CPU and GPU coolers, are also present. That said, we feel that when performance is otherwise equal, you're better off purchasing the quieter power supply.
One power supply is completely inaudible during the 100W and 300W tests in our soundproof box: the Corsair RM Series 650W. Another two models are nearly equally silent – our microphone registers a tiny amount of noise, which is probably caused by the electronics. Regardless, as long as you don't draw 500W from them, both the Seasonic Platinum Series V2 and the Seasonic X-Series V2 are essentially inaudible. That said, only seven models exceed the 30 dB(A) threshold during the 100W test.
While we'd expect that studying the performance at 300W would reveal larger differences, we end up with a largely similar situation. Only during the 500W test do we observe clear differences. Keep in mind that you'll generally not draw this much power from these PSUs. However, if silence is especially important to you, the Seasonic X-Series V2 makes for an excellent choice, as it only generates 20 dB(A) of noise, even after outputting 500W continuously over the course of 20 minutes. The Corsair CS-M Series 650W, the Be Quiet! Dark Power Pro 650W, and the Super Flower Leadex Gold 650W are very quiet as well. The Corsair RM Series 650W is also far from noisy, as it only produces 30 dB(A) during this test.
The power supplies that bring up the rear are far from quiet, however. The Codegen Super Power produced 50 dB(A) during the 300W test and perished during the 500W test. The Antec Neo Eco 620C doesn't impress either, with 46 dB(A) at 300W. Fractal Design's Integra M 650W and Seasonic's M12II Bronze 620W exceed the 50 dB(A) threshold during the most demanding test. Most of the other models remain below 40 dB(A), and thus aren't particularly noisy during regular use.