noise level

Hi all

Please can someone explain to me how the noise level is calculated when I load in a spectrum? I have compared it to the maximum value and the standard deviation of an empty region in Azara, and the V3 Assign number is always higher. The peak intensity is more or less the same so its not a scaling issue. Should I be calculating the noise level myself outside CCPN and changing the noise level?


Hi Helen,
The noise level is calculated as the mean + 3.5 * SD from a portion of the spectrum without signal . You can see by right clicking in a spectrum display, then select estimate noise.

I can suggest a way to visualise/edit graphically from a 1D slice.
Update to the latest version first.

  • Select an nD peak, run the macro extractSliceAtPeakPosition from the built-in macros (or find it in the macros section in the forum).
  • This will create new 1D spectra (depending on the original peak dims).
  • Open a new 1Dspectrum in a new display
  • right click and select show noise thresholds
    • this will show negative and positive noise levels as a horizontal line
  • you can also modify it by selecting the line, and dragging up-down to set a new value.
  • if you do this, the noise is set only to the 1d spectrum, obviously. but you can simpling amend the nd spectrum by doing:

get(‘SP:spectrumND_name’).noiseLevel = get(‘SP:spectrum1D_name’).noiseLevel