How to calculate SNR of signals in MATLAB? -

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i've encountered simple, yet fundamental problem on calculating snr:

there several signals :

  • s1 = original , pure clean signal without noise.

  • n1 = white gaussian noise going added s1.

  • s2 = s1 + n1 (the noisy signal before performing noise-reduction algorithm)

  • s3 = noise-reduced signal (after performing noise reduction algorithm)

  • n2 = s3 - s1 (the amount of noise after performing noise-reduction algorithm)

now want compare snr before , after performing noise-reduction algorithm.

  1. which signals should consider snr_before!? s1/n1 or s2/n1 ?

  2. which signals should consider snr_after!? s3/n1 or s3/n2 ?

  3. which commands or functions should use in matlab in order compute snr_before , snr_after?

thanks billion putting time on helping me.

what know calculating snr before :

snrbeforenoise = mean( signal .^ 2 ) / mean( noise .^ 2 );

and snr after :

residual_noise = signal - noise_reduced_signal; snr_after = mean( signal .^ 2 ) / mean( residual_noise .^ 2 );


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