One-Third Octave Filtering of Low Frequency Data

[DiggerICT]

I would like to analyze steady state, low frequency (0.1Hz to 80Hz) data that has been aquire over several minutes of acquisition at a rate not exceeding 1000Hz. I am using the Third Octave Filtering Tools in the Signal Processing Toolkit, but it is unclear to me that if I just change the sample rate input into the Third Octave Filtering.vi if that will give me the octave bands that correspond to the ranges that I am interested in. Is the any other way to calculate this? For example, if I wanted to find the band power of an individual octave band, say band 0, which has a center frequency of 1Hz, how would I do that?

[Jack_A.]

There is a thorough explanation of the algorithms and details of the ANSI S1.11-1986 specification to which the toolkit is built around in the reference manual for the Signal Processing Toolkit. Here is a link to it:

http://www.ni.com/pdf/manuals/322142a.pdf

On page 24-4, it explains how to calculate the center frequencies of your 1/3 Octave filter bands.

Jack Arnold
Application Engineer
National Instruments

[Jack_A.]

I would like to discuss this with you in a more private forum. Could you email me at jack.arnold@ni.com?

Thanks,
Jack Arnold
Application Engineer
National Instruments