Normalization by maximum PSD value while calculating frequency based HRV metrics

[himalayajung]

I understand the rationale to normalize PSD values by the maximum PSD value since it makes it easier to compare different PSD methods (at least visually). (normalize=True is the default value in https://github.com/neuropsychology/NeuroKit/blob/master/neurokit2/hrv/hrv_frequency.py) However, doesn't the normalization change the PSD values and hence the frequency HRV metrics values? Also I think it changes the unit of PSD?

Is normalization recommended while calculating frequency HRV metrics?