SNR for hercules 'diff2' consistently lower than 'diff1' & 'sum'

is normal/expected that the SNR value for the ‘diff2’ combination will always be significantly lower than the SNR for the sum or ‘diff1’ combinations for hercules data? I also consistently see some noise in the 4 ppm range in many of my subject’s data (see attached picture from osprey), are the data still usable despite this, or this going to make the data unusable?

Hi sdw,
the definition of SNR in Osprey is: ‘SNR is determined as the ratio between the amplitude of the NAA peak and the standard deviation of the detrended noise between −2 and 0 ppm’. I’m not very familiar with HERCULES, but in one difference spectrum you have the NAA peak (e.g. contains A + C or - A - C) and in the other not (e.g. contains A - C or - A + C) . I guess, that would explain the differences in SNR.
Unfortunately, I also know these spurious echoes at 4ppm. Maybe from not perfect suppressed water, but I’m not sure.

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