From: Jim Peters (jim_at_uazu.net)
Date: 2002-02-15 09:15:13
Jim Meissner wrote:
> > buried in EEG recordings that we might never have seen before
>
> I spent 10 years going down that path, thinking like you, there
> "must" be some magic frequency in there somewhere. That is what
> drove me to spend the time building my own EEG because I was able to
> see the flaws in all the other approaches. In some ways that itch
> is still there. I am quite willing to have another go at it. If
> your post filtering finds some magic data, I will not be unhappy
> just because I could not find it. My main caution is to run a clean
> system that does not create artifacts. White noise and impulse step
> functions run through sharp filters will show data that is not
> really there. Normal beta brain waves are just random noise.
My approach is that I want to see exactly what is there, in as much
detail as possible. Obviously I don't want to be creating artifacts
because I'm trying to create a reliable tool. In my code I'm trying
to take the most direct path from the source signal to the displayed
data, and I'm trying to make everything that might fail, fail in a
predictable way. I'm also accustomed to writing code that doesn't
need too much debugging, by keeping the number of 'special cases' in
the code to a minimum.
Step functions and noise are already obvious on my existing filterbank
output because they span the entire frequency range. They should be
even more obvious on the output of the new tool.
> I see that you have been able to run my files on your system. Take
> a look at the Test.dat file more carefully. I purposely modulated a
> sine wave tone various ways to see what the FFT did with it. Look
> at that with your voice print and or filter scheme. Make sure your
> system does not "create" things that are not there.
Yes, I saw some of that -- turning it on and off and stuff. I'll take
another look once I've got the front-end of this app written and
working.
> The data that I would like to go over with a fine toothed comb is
> the file "Downey.dat" on my webpage. At some point during that
> session the medium in trance stated: "Look at these frequencies that
> are coming through right now, those are the ones you are looking
> for!" I will tell you more about that session when you are ready.
Great! You know, it's my curiousity that is driving me. I look at
the output of my filterbank, and I can see some things, but I want to
see *between* the traces to see if these are static frequency waves,
or sweeps, or varying frequency waves, or maybe as you say, just
random noise. This is what I plan to do.
I'm not looking for 'magic' frequencies. I just want to see what is
there.
Jim
-- Jim Peters (_)/=\~/_(_) jim_at_uazu.net (_) /=\ ~/_ (_) Uazú (_) /=\ ~/_ (_) http:// B'ham, UK (_) ____ /=\ ____ ~/_ ____ (_) uazu.net
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