fractional transfer function

[ankit]

Hello

I am using Frequency response function from sound and vibration toolkit and getting Magnitude, Phase and Linear frequency. I want to do the frequency response function in such a way that I get my results in fractional octave analysis (meaning I want the magnitude, phase averaged for that particular frequency band octave, 1-3 octave).

Again Frequency response function where the frequency scale is not linear but represents 1-3 octave bands and the appropriate values for magnitude and phase.

Any suggestions

Thanks

Ankit

[BrowningG]

Hello Ankit,

The Sound and Vibration toolkit contains several VIs and examples for performing octave analysis.  The manual for this toolkit has several pages of information on octave analysis (start at page 10-1).  There are also several shipping examples with the toolkit that provide some great getting started information.  From LabVIEW click Help -> Find Examples.  This will open the NI Example Finder that locates all of the shipping examples installed on your computer.  Follow the path Toolkits and Modules -> Sound and Vibration -> Analyzing and Processing Signals -> Octave Measurements.  In this folder there are several examples that use the octave analysis VIs for performing a magnitude measurement. 

You can find the VIs used for octave analysis by searching for “octave” from the functions palette or by following the path Addons -> Sound and Vibration -> Octave Analysis in the functions palette.  These VIs do not perform a phase measurement for the octave analysis, so it would necessary for you to write your own algorithm to analyze the phase of the octave bins. 

[BrowningG]

Hello again Ankit,

From your first post, it looked like you would be OK with the scalar quantity that the octave analysis VIs provided.  From your other posts, it looks like it is more important that you have the magnitude and phase of each octave.  The Sound and Vibration Toolkit VIs currently provide FRF for linear frequency bins.  The octave analysis VIs provide power levels per octave, but not the magnitude and phase information you are looking for.  As a result, it looks like you will have to do some of the programming yourself.  Could you provide some more details of what you are trying to do exactly?  With a better idea of your application, it will be easier to help you out.   

[ankit]

Hello Browning

I am trying to write an application for the purpose of calculating the sound absorption coefficient of materials in an impedance tube. I wanted to if the data (absorption coefficient )has to be reported in Octave bands (1, 1/3, 1/.6 or any other required one) then is it possible to get the transfer function's magnitude and phase for each bands. But now after doing a little research I think it is not possible conceptually to get phase for a band. But I am not a GURU in this , I may be wrong but for now wher I stand I think one cannot calculate the phase for a band.

Octave bands are defined for averaging SPL's not for phase.

Thanks for taking interest in my post.

Ankit