How is the intensity of sensor noise determined experimentally?
I would think using an FFT or Spectral Density Analyzer is the most common way to measure noise to determine the amplitude and see if it is Gaussian or filtered Gaussian (Brown or Pink or White noise for example) or if there is a DC component...
The filtering to obtain maximum SNR ought to be matched to pass the spectral density of the signal and inversely matched or attenuated to spectral distribution of noise to obtain the ideal S/N ratio.