Noctua CPU cooler low noise adapter

[Ad Hominem]

The Noctua NH-D15 just arrived in the mail today, and my plan is to install it tonight once my son is in bed for the night. Looking through the instructions and parts, I see that there is a Y splitter so you can feed both fans from a single CPU fan header.

The part of this that I'm not sure about is the "Low Noise Adapter" (LNA). What is the use case for these? Are they to reduce electrical noise and interference with other circuits or is it some kind of in line resistance that would lower voltage to the fans, making them spin slow, thereby making less physical sound?

[r.linder]

It's probably just for acoustics. If you don't care about noise, you don't need it.

[Omega]

The LNA will make the fans spin slower to reduce noise. They will be included with the cooler as separate cables.

[Overseer]

Its really just a resistor that lowers electric charge at the other end. So whatever you set in BIOS/software gets scaled down. Effectively making it impossible to reach max RPM with the benefit of having lower RPM at all settings.
If you use a custom fan curve on a PWM fan its pretty pointless. But it may be useful if you want to optimize cooling and noise.