The following thresholds can be set to sort out noisy spectra.
noise to signal ratio:
Maximal noise to signal ratio of a spectrum considered for analysis. The noise is defined as the rms difference between the low-pass filtered spectrum and the orginal spectrum. The signal amplitude is the maximal intensity of the spectrum.
background to signal ratio:
Maximal background to signal ratio of a spectrum considered for analysis. The background is defined as the intensity at the edges of spectra window. The signal amplitude is the maximal intensity of the spectrum.
relative intensity threshold:
Minimal integrated intensity in percentages of the average integrated intensity