R128

Here is the EBU R128 standard for measuring "dynamic range" that Roon uses:

https://tech.ebu.ch/docs/tech/tech3342.pdf

Dynamic range can mean different things.  In the context of technical measurements of an amplifier or transmission system, dynamic range is pretty similar to "Signal to Noise."  What is range from the lowest signal that can barely be resolved to the maximum.  So a dynamic range of around 120dB is where many of the best units are (chips can be as good as 130dB).

But this has nothing to do with they "Dynamic Range" of program material.  But what has long bugged me is, what does this mean anyway, because every signal, no matter how high the peak, ultimately has to go back through zero again.  And how close it gets to zero depends on how finely you can measure it, assuming it's a continuous waveform.  So this is back to to the "dynamic range" of amplifiers again.

But this is not what audio/music people mean by the Dynamic Range of program material.  Their window of analysis is not 1 uS, say, the resolution of a decent digital scope.  Their resolution is the loudness in a 3 second time window which must be overlapping.  The spec is unclear to me, but in specifying "dBFS" it is clear to me they don't mean instantaneous levels but something like average or probably RMS levels...that is to say levels related to the equivalent sine wave measured with RMS.

And then the Dynamic Range is specified as the difference between the 10th percentile and the 95th percentile of these 3 second time windows.

Now it's still not clear to me how Roon uses this in level normalization.  There must be other parameters such as the maximum level, etc, because the R128 I've just described only relates to relative and not maximum levels.