adding noise 15 db

hi everyone.. i want to ask something..

this is my source code..

t=0:0.01:5;

num= [0 0 0.31185 8.28 55.2];

denum=[0.001088 0.044 0.69185 9.28 55.2];

sys=tf(num,denum);

step(sys,t)

grid

title ('Unit-Step Response')

xlabel('t')

ylabel('Amplitudo')

how to adding noise 15 dB to this coding? thanks for your help

Answer 1

[Greg Heath]

I don't know about your coding. However, I add Gaussian noise to a noise free signal, s0, as follows

P0 = mean(s0.^2)

SNR = 10^(SNRdb/10)

s = s0 + sqrt(P0/SNR)*randn(size(s0));

Hope this helps.

Greg

[Souarv De]

What is s0?

[anass naqqad]

It's just the noise free signal