add white gaussian noise to signal

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rohollah hosseyni 2021-2-26

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https://ww2.mathworks.cn/matlabcentral/answers/756809-add-white-gaussian-noise-to-signal

评论： rohollah hosseyni 2021-2-26

the original siganl is right above iamge and left above image is my output, that's not my problem but the paper says "The Gauss white noise is added to the signal when signal to noise ratio is 5dB".

I try to build b prime image in the right bottom corner but my output is b image. I use " awgn(x,SNR) " with SNR=5, but output image is not like b prime image.

I know my output image shouldn't be exactly like b prime image because of randomness property of noise, but my b image is not like b prime image in terms of magnitude and appearence and ..., does anyone know why?

N=512;  n=1:1:N;
y=4*cos(8.*pi*n./N)+(N/5);
x=cos(2*pi.*y.*(n/N));
subplot(2,1,1)
plot(n, x); axis([0 512 -1.5 1.5]); title('x')
xn= awgn(x,5);
subplot(2,1,2)
plot(n, xn); axis([0 512 -1.5 1.5]); title('x+white guass noise')