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Reply-To: "Nasser Abbasi" <nma@12000.org>
From: "Nasser Abbasi" <nma@12000.org>
Newsgroups: comp.soft-sys.matlab
References: <gj1lke$nlp$1@fred.mathworks.com>
Subject: Re: Separated the noise
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Date: Thu, 25 Dec 2008 21:12:35 -0800
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"Muhammad " <fahrudin_fistek@yahoo.com> wrote in message 
news:gj1lke$nlp$1@fred.mathworks.com...
> dear who considering
>
>
> i write my simple code under my simple information of matlab function
> and post the code in order to benefit other beginner
> thanks
> I have a problem and I hope any help for me
>
> how to separated the original signal from its noise.
>
> I have a  wave(.wav)
> I blend it with noise.
> my listing program :
> y=wavread(open.wav);
> spect=abs(fft(y,1024));
> frek= linspace(0,22050,512)
> plot(frek,spect(1:512));
> % generate and mix the noise.
> open_noise=agwn(y,20);
>
> Thank you.
>

That is probably going to be a very hard to thing to do I would think. To 
separate WGN from the signal, that is.

White Gaussian noise has a constant power spectrum which extends over all 
frequencies, hence direct filtering would not work.

In addition, if you were able to remove WGN from the signal somehow, this 
means you have solved THE communication problem itself, and the Shannon 
channel limit do not exist since noise is no longer an issue in 
communication as one can extract the original signal.

May be you can, using statistics, and assuming you know the spectrum of the 
original signal and may be other assumptions,use Wiener filter to reduce 
WGN. But again, I do not think it is possible to eliminate WGN from a signal 
completely and in general under all conditions.

I could be wrong ofcourse.

--Nasser