The Noctua NH-D15 cooler comes with two NF-A15 fans in a pack version. These two fans are perfect for cooling this cooler. They are very powerful since by default they blow at 1100 RPM (rotations per minute).
However, such a speed necessarily generates noise. We hear a constant “VOO-VOO”. And it gets worse in the old cases that make resonance. So how to reduce the noise of the fans?
Via the Bios
The NF-A15 comes with two cables, a LN (low noise) and an ULN (ultra low noise). Try the LN first and if that is not enough, add the ULN. If there is no difference, go to the BIOS (at startup F8 or del or other key: read the screen to know: F1, F2 or F12). Then locate in the FAN Control Through Bios, CPU Smart FAN Control or CPU Smart FAN Target options, enable it. The motherboard should then manage the fans smarter and push them fully only when the processor starts to heat or the load becomes important.
Via a software
If your motherboard is old and does not have this option, then you have to go through software. Such as SpeedFan, the most widespread. It will be necessary to adjust the fan so that the noise disappears. With about 60-70% in PWM1. When you launch an application or a greedy game, it will be necessary to put it again at 100%. The problem is that it will constantly launch at each new start, which can quickly become boring. You can always add a shortcut in the start menu and set automatic fan speed.
Via an external controller
There are external fan speed controllers at correct prices that will do the job automatically.