The Mel scale attempts to describe how humans perceive frequency difference at different frequencies. When using a mel-scaled filterbank this determines the pos

The Mel scale attempts to describe how humans perceive frequency difference at different frequencies. When using a mel-scaled filterbank this determines the position of each filter on the frequency axis. Which is closer to logarithmic than linear. Mel-scale is commonly used in spectrograms when doing machine learning on audio. Common alternatives would be the Bark scale, 1/3 octave filters, or Gammatone filters. The spacing of filters is not the most critical in a loudness calculation though, but instead what loudness weight to have at the different frequencies. In EBU R128 the k-weighted curve is used. This is very smooth across frequencies. So if one were to implemented this in spectrogram (time-frequency) domain with a filterbank, one could do a decent job in any of the above mentioned frequency scales. If a standard would recommend something like that, I think 1/3 octave bands would be chosen, because it is standardized in IEC 61260. Whereas Mel scale is not standardized by any formal body (that I know). But I believe the k-weighted in EMU R128 is is most commonly implemented by in the time-domain, which means that there is no need to have a filterbank with discrete frequency resolution.