I bought this fan to 4 son (PWM) to replace the 3 son of my cooler Noctua NH-U12F. It is apparently too powerful for my motherboard, since its minimum speed of 200 rev / min (the maximum is 1300) is interpreted by the cold start to the BIOS as a malfunction ... That said, it works inaudibly and runs at ~ 700 t / min cruising speed, where my Noctua turned to 1300. Its characteristics are 26.5 and 74.25 dBA max max CFM We'll see with time, but for now it appears very good to me.