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Thread: Removing noise by superimposing quasi periodic bio-medical signals

  1. #1
    Associate Engineer
    Join Date
    Sep 2012
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    1

    Confused Removing noise by superimposing quasi periodic bio-medical signals

    Hi everyone,

    I'm fairly new to signal processing. I'm doing a project which involves using matlab to superimpose quasi periodic bio-medical signals (emg or egg signals) to remove the noise (the noise approaches zero because its mean is zero) so I can calculate the signal to noise ratio (SNR). The problem is that I think the frequency changes over time (quasi periodic) so I don't know how to superimpose them. Is there a way to superimpose signals with different frequencies to cancel noise or is there an algorithm to change frequencies. How should I do it? I'm very confused. Thanks in advance.
    John

  2. #2
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,043
    Not fully understanding what you require, I would suggest you look at a tracking method if the frequency is changing during the test duration. There will be transitions as the frequency changes and the only way I can think of is to actively track the frequency as is done in active-noise-cancelling headphones. Only then will you be able to ascertain any SNR.

    I cannot see it being done in something like Matlab unless you can create a script to follow the frequency and that sounds like a very complex undertaking to me.

    But, then, I have been wrong before.

  3. #3
    Principle Engineer
    Join Date
    Mar 2011
    Posts
    175
    John,

    Looks like homework and a lack of understanding of the process.

    You can't remove noise from a signal by what you say you are trying to do.
    It would remove the signal as well. And your S/N will = 0/0

    So, I suggest you get a better understanding of signal processing and spectra to attack the noise.

    The problem has no place on this forum.

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