Inconsistent PSD depending on window length

Francois · January 24, 2021, 8:11am

Windowing code:

brainstorm-tools/brainstorm3/blob/master/toolbox/timefreq/bst_psd.m#L94


% Check if this segment is outside of ALL the bad segments (either entirely before or entirely after)

if ~isempty(BadSegments) && (~all((iTimes(end) < BadSegments(1,:)) | (iTimes(1) > BadSegments(2,:))))

    disp(sprintf('BST> Skipping window #%d because it contains a bad segment.', iWin));

    Nbad = Nbad + 1;

    continue;

end

% Select indices

Fwin = F(:,iTimes);

% No need to enforce removing DC component (0 frequency).

Fwin = bst_bsxfun(@minus, Fwin, mean(Fwin,2));

% Apply a hamming window to signal

Win = bst_window('hamming', Lwin)';

WinNoisePowerGain = sum(Win.^2);

Fwin = bst_bsxfun(@times, Fwin, Win);

% Compute FFT

Ffft = fft(Fwin, NFFT, 2);

% One-sided spectrum (keep only first half)

% (x2 to recover full power from negative frequencies)

% Scaling options

switch PowerUnits

% Physical units, amplitude independent of window length