Now noise testing is basically done twice, once with the fans cranked up to 100% and again at 50%. Depending on how good the cooling performance it is possible that the fan or fans will run even lower than 50%, but to be consistent these are the two testing points. So the NF-A9x14 PWM used in the NH-L9a-AM4 is used in three of the heatsinks tested so the results here weren’t a big shocker. It runs in the middle of the pack at 100% fan speed but is much quieter at 50%. This is because of its higher max RPM. Sadly because of the smaller heatsink size, this one is also a lot more likely to run in the 50-100% range, especially when paired with a higher end CPU. The NH-L12S, on the other hand, has a new NF-A12x15 PWM. This is the thin 120mm design that Noctua spent years getting out. So I was really curious to see how it would perform. In the end, it was similar to its smaller brother. I was hoping that 100% fan speed noise would be lower but it ended up being a little higher. Still good when compared to the competition, but that is expected with Noctua products in noise testing. The L12S, however, is a LOT more likely to run cool enough that the fan runs much lower.