Third octave analysis giving very close but in accurate results

I am having troubles with 1/3 octave analysis. I have recorded a calibration tone of 94 dB in B&K Pulse and exported a time series that is Pa values, an AC signal of 1.414 peaks over a time period of 15s.
When loading this CSV file and passing through the third octave module I get 94.6 dB at 1kHz and overall sound pressure of 94.6 dB. However the Labview output, especially in the lower bands, of the third octave anaysis are up to 10 dB out from the pulse measurement.
The settings, averaging type (linear), weighting (linear) are the same and yet the values of the thrid octave output are very slightly different. I can provide code and the Pulse output - i wonder if anyone else has has similar problems?
Any help is appreciated.
Thanks Greg

Hello Greg,
I cannot say that I have seen a similar problem. Which version of LabVIEW are you using? Which Sound and Vibration option have you installed?
There are several examples that ship with LabVIEW for Octave analysis. Did you start with one of the examples from Example Finder to build your application, or have you created one entirely on your own?
Providing the code would be helpful. Please post the smallest piece of code that can be used to replicate the issue.
Regards,
George T.
Applications Engineering Specialist
National Instruments UK and Ireland

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I’m working about third octave decomposition with a vibration signal.
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Bastien

thank...
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Third octave operations with "sound and vibration toolkit"

Hi!
I’m working about third octave decomposition with a vibration signal.
I’m using the sound and vibration toolkit.
The sample frequency of my signal is 2400 Hz.
And I’m working with a 1 second vibration signal (so 2400 points).
Fs = 2400
N = 2400
I need to understand the different and successive operations that the “SVT Fractional-octave Analysis [IEC].vi”VI do.
In fact, I think that my frequency resolution (df = Fe/N=1Hz) is too low.
Do you have a solution?
Maybe I could turn into my 1 sec signal in 10 sec signal with 10 recopies and assemblage of my previous signal?
N’ = 10N so df = Fe/10N = 0.1Hz.
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Third octave analysis giving very close but in accurate results

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