EZ Chrom signal to noise

[carbontritium]

Any ideas on why I get two different results for S/N ASTM depending on if I integrate only the peak of interest, or the peak of interest and a previous peak? As ever, the EZ Chrom help is of no use whatsoever

[HPLCaddict]

If you integrate only the peak of interest, everything else that's near this peak will be seen as noise by EzChrom. If there are other peaks present, no matter if they are system peaks, injection noise, gradient humps or "real" analyte peaks, is interpeted as noise so your s/n ratio will be really small. If you integrate these peaks, they are not considered noise anymore for EzChrom, so s/n gets higher.
AFAIK the EzChrom help explains which area of the chromatogram around the peak of interest are used for noise calculation. The explanation above of course only applies to peaks found in this area.