– Noise Method is the method you can choose to add some procedural noise to your simulation.
– In older Blender versions this parameter was in the Hight Resolution Tab and you could choose between FFT or Wavelet.
– In 9.2 (stable) the only method available is Wavelet.
– You can control how the Wavelet is applied to your smoke/fire by setting some parameters in this tab.
– You can find some information about the code used by Blender (WAVELET_NOISE.h) here:
– and here: