ThirdOctaveAnalysis (FPScript)
Carries out a third octave analysis for an amplitude spectrum.
Syntax
ThirdOctaveAnalysis(Spectrum, Result)
The syntax of the ThirdOctaveAnalysis function consists of the following parts:
Part |
Description |
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|---|---|---|---|---|---|---|---|---|---|---|---|
Spectrum |
The data set with the amplitude spectrum to be evaluated. Permitted data structures are signal und signal series. All numeric data types are permitted. For the X component additional restrictions do apply.The values must have a constant positive spacing. For complex data types the absolute value is formed. If the argument is a list, then the function is executed for each element of the list and the result is also a list. |
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Result |
Specifies whether the mean value of the amplitudes assigned to a third octave band is to be taken or whether the amplitudes are to be summed up. The argument Result can have the following values:
If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated. |
Remarks
The frequencies of the amplitude spectrum are divided into frequency bands and their mean is taken or they are totaled. The function enters the mid frequencies of these frequency bands in the X component of the result. The following table shows the cut-off frequencies and the mid frequencies of the frequency bands:
Third octave bands |
||
|---|---|---|
fm |
fl |
fh |
... |
||
1 |
0.894 |
1.118 |
1.25 |
1.118 |
1.414 |
1.6 |
1.414 |
1.789 |
2 |
1.789 |
2.236 |
2.5 |
2.236 |
2.806 |
3.15 |
2.806 |
3.550 |
4 |
3.550 |
4.472 |
5 |
4.472 |
5.612 |
6.3 |
5.612 |
7.099 |
8 |
7.099 |
8.944 |
... |
The above frequencies continue periodically across higher orders of magnitude.
Available in
FlexPro Basic, Professional, Developer Suite
Examples
ThirdOctaveAnalysis(FourierSpectrum(Signal, SPECTRUM_AMPLITUDE), AMPLITUDE_RMS) |
Calculates the RMS third octave spectrum of a signal. |