This will add normally-distributed broadband random noise to your EEG signal vector:
sd = 0.1; % Standard Deviation Of Random Noise Vector
normal_noise = sd*randn(1, N); % Create Normally-Distributed Random Noise Vector With Standard Deviation = ‘sd’
noisy_EEGsig = EEGsig + normal_noise; % Add Noise To ‘EEGsig’
