[FieldTrip] Spectrum normalization

[Jack Fogarty]

Hello,

I've been looking for some clarification on the normalisation and scaling applied in ft_freqanalysis through the subfunctions like 'ft_specest_mtmfft'. I have not been able to find specific explanations of these transformations and their application to EEG online, are there any known readings/explanations available?

I am hoping to determine:


  1.  Why the taper is normalised like this:   tap = tap./norm(tap, 'fro');    (e.g., in ft_specest_mtmfft [line 221])
  2.  Why the FFT output is scaled like this: dum = dum .* sqrt(2 ./ endnsample); (e.g., in ft_specest_mtmfft [line 277])

I can see this same question was asked some time ago, but no further details were added to this thread. If anyone can clarify these transformations it would be much appreciated!

Cheers,

Jack Fogarty
PhD Student

T:  +61 4221 5547  |  E:  jf752 at uowmail.edu.au<mailto:jf752 at uowmail.edu.au>

Brain & Behaviour Research Institute
Psychophysiology Lab | School of Psychology | University of Wollongong
[cid:image001.png at 01D70F45.E786A500][UOW shield bl]

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