Question on envelop_hilbert algorithm in BioSigKit

[longluu]

Hi Hooman,

Thanks for making the BioSigKit open for the scientific community. I have a few questions about the function 'envelop_hilbert.m'.

• On line 113: you have this:
  if ~isempty(nois_buf)
  Because you initialized nois_buf with a zero array so I think it should be always true. So I wonder if you actually mean to check if there is non-zero values in the nois_buf? If it's the case, I guess we have to use a different condition checking.

• Line 88-93:

if threshold_style
   THR_SIG = 4*mean(env);
end

nois = mean(env)*(1/3);                                 % noise level
threshold = mean(env);                                  % signal level

Here you set initial values for threshold, noise and signal level based on the mean of Hilbert envelope. As I understand, the envelope mean is 0 (from line 77 env = env(:) - mean(env); ) so all of those values will be 0. I just want to confirm with you if that is the case.

• Finally, just a general question. Do you have a reference for this algorithm somewhere so I can read in more detail the theory behind this?

Thanks again for you contribution. I'm looking forward to hearing from you.

Best,

Long