Thank you Daniel. I wish to calculate SNR for i traces as given by this equation: 
where ai is the amplitude scaling factor, si is the signal in the trace and ni is the noise. I expect to see arrays of SNR for i traces.
I also need a code to calculate PSNR using this equation: 
where Pi is the peak value of si in the first equation and sigmal is the variance of the noise in the first equation.
I attach the material in pdf that shows what I am trying to do.
This is what I have so far:
SNR := Table[
10Log[a[[i]]^2Norm[trs[[i]]^2, 2]/Norm[s[[i]]^2, 2], 10], {i,
Length[trs]}];
P := Max[trs[[i]]];
PSNR := 10*Log[(a[[i]]^2 P[[i]]^2)/s^2, 10], {i, Length[trs]};
{SNR[[1]], PSNR[[1]]}
Attachments:
