Proper way to add noise to signal

Question

In many areas I have found that while adding noise, we mention some specification like zero mean and variance. I need to add AWGN, colored noise, uniform noise of varying SN

Answer 1

This 'should not divide by 0' problem could be easily solved if you add a condition to check if targetSNR is 0 and do these only if it is not 0. When your target SNR is 0, it means it's pure noise.

function out_signal = addAWGN(signal, targetSNR)
sigLength = length(signal); % length
awgnNoise = randn(size(signal)); % orignal noise
pwrSig = sqrt(sum(signal.^2))/sigLength; % signal power
pwrNoise = sqrt(sum(awgnNoise.^2))/sigLength; % noise power
if targetSNR ~= 0
   scaleFactor = (pwrSig/pwrNoise)/targetSNR; %find scale factor
   awgnNoise = scaleFactor*awgnNoise; 
   out_signal = signal + awgnNoise; % add noise
else
   out_signal = awgnNoise; % noise only
end