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Testlab: Lower octaves missing? (especially for 1/24th octave)

Creator
Creator

When I display my data as octaves, the lower octave bands do not show.

 

For example, with 1/3 octave, I only see data down to 50 Hz octave band.  Would like to get to 20 Hz octave band.

 

third-octave.png

I processed the data with a 2 Hz resolution, frame of 0.5 seconds, stationary tracking, energy average.

 

Displaying in 1/24th octave only shows to 350 Hz octave band.

24th-octave.png

 

2 REPLIES 2
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Re: Testlab: Lower octaves missing? (especially for 1/24th octave)

Siemens Phenom Siemens Phenom
Siemens Phenom

If you are using the octave display to view narrowband data, there is a requirement in Testlab to have at least 5 spectral lines worth of data per octave.  Because the lower frequency octave bands are narrower, it is not always possible to get 5 spectral lines within the band.

 

Under "Tools -> Options -> General" of Testlab, this requirement can be modified.  By switching "Minimum spectral lines for octave band" from 5 to 1, more bands will be calculated.

 

options2.png

 

If this is not sufficient, then the data will need to be reprocessed with a finer frequency resolution.

Re: Testlab: Lower octaves missing? (especially for 1/24th octave)

Creator
Creator

I switched from 5 spectral lines to 1 and my missing octave bands appeared instantly:

 

all_octaves.png

 

Thanks