I know that it's RMS signal V/RMS noise V, but how do I know the RMS noise voltage?

 

I know that it's RMS signal V/RMS noise V, but how do I know the RMS noise voltage?

What are the two signals being displayed? Without that information it means nothing to me.

 

What are the two signals being displayed? Without that information it means nothing to me.

Never mind, I realised it’s pretty impossible

 

The solution is to work in the frequency domain with FFT function that i suppose you have in many of digital scope.
Jean-Louis