Extract a signal from noise, so I can view noise spectrum only?

1. How do you identify noise in a signal?
2. What can you say about correlations and detection of signals buried in noise?

How do you identify noise in a signal?

Therefore, to ascertain the signal to noise ratio, one must find the quantifiable difference between the desired signal strength and the unwanted noise by subtracting the noise value from the signal strength value.

What can you say about correlations and detection of signals buried in noise?

We can correlate the signal plus noise with a copy of this waveform, and then average. The noise does not line up with the correlating waveform so adds as power. The signal does correlate, so adds as voltage, leading to a 3dB improvement in SNR each time the number of averages is doubled.