# How to Combine white gaussian random noises from different Seeds?

I have generated two different white gaussian random noises in MATLAB using two different seeds. For example:

Asn1 = sqrt(noisepow1/2)* (randn(size(As))+1i*(randn(size(As))));
Asn2 = sqrt(noisepow2/2)* (randn(size(As))+1i*(randn(size(As))));


Here, noisepow1 and noisepow2 are amplitudes of noise powers, As is signal array.

I will need to add these two noises to calculate the SNR. As the two noises are from different sources, I am confused about how to add these two noise signals. I can't simply just add Asn1 and Asn2 to calculate the total noise, because some signal samples will have opposite phases. Should I add like below:

AA =  sqrt(noisepow1/2).*(randn(size(As)));

BB =  sqrt(noisepow2/2).*(randn(size(As)));

Asn = AA+BB + 1i*(AA+BB);


I am confused about the addition operation of these two white Gaussian random noise signals. Any suggestion would be helpful.

So, yes, you simply add the noises, and if you're doing it right, then the resulting noise will have variance noisepow1+noisepow2.