how to add non uniform Noise

I have tried generate non uniform noise matrix using matlab. To add it with source signal matrix 13 by 13. Please feel free to share your idea about non uniform noise matrix addition.

Answer 1

[Ameer Hamza]

What about multiplying the noise matrix with another function. For example

M = randn(13);
[~,~,Z] = peaks(13); % peaks is just used as an example
M_new = M.*Z;

subplot(2,1,1);
imagesc(M);

subplot(2,1,2);
imagesc(M_new);