Limit testing on frequency/band power (octave analysis) data

I have performed an octave analysis and displayed the result in a regular XY-graph. The frequency appears on the x-axis and these values are not linear (they appear to be logarithmic). On the y-axis there is band power expressed in dB. I would like to perform a test to see if the graph falls within a certain region of the graph area. I would like to define this region using a small number (i.e. much less than there are octave analysis points) of XY-value pairs and then have LabVIEW interpolate in between these XY-value pairs to come up with a well-defined region in the graph. How can I do this? I'm using LabVIEW 8.2.1 with the Sound and Vibration add-on. I'd greatly appreciate any hints.

Of course.
20.3   -133.49
21.5   -145.84
22.7   -135.988
24.1   -133.697
25.5   -140.965
27   -122.645
28.7   -141.809
30.4   -135.857
32.2   -141.348
34.1   -128.545
36.1   -134.527
38.3   -136.317
40.5   -128.509
42.9   -128.973
45.5   -136.79
48.2   -122.849
51   -113.688
54   -122.504
57   -126.121
61   -134.923
64   -128.324
68   -129.938
72   -130.799
77   -123.386
81   -111.166
86   -126.693
91   -132.977
96   -126.776
102   -117.21
108   -105.319
115   -124.972
121   -129.746
129   -127.194
136   -129.205
144   -120.787
153   -112.319
162   -119.499
172   -129.217
182   -129.23
193   -122.976
204   -116.798
216   -112.12
229   -127.912
243   -125.158
257   -123.813
273   -122.386
289   -126.322
306   -122.785
324   -111.216
343   -123.328
364   -123.024
386   -119.788
408   -114.873
433   -113.137
459   -121.081
486   -116.245
510   -117.301
550   -113.945
580   -120.074
610   -117.581
650   -114.84
690   -118.394
730   -120.486
770   -114.674
820   -119.4
870   -112.691
920   -117.804
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1030   -120.331
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1160   -118.436
1220   -118.786
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1460   -119.648
1540   -115.799
1630   -115.615
1730   -116.24
1830   -115.901
1940   -116.705
2060   -115.644
2180   -117.336
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2450   -116.72
2590   -115.973
2750   -115.929
2910   -118.224
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4620   -119.149
4900   -119.276
5200   -118.173
5500   -118.282
5800   -118.231
6200   -118.621

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How to calculate power in specific frequency band

Hi Everyone. I have been trolling on here for months but this is my first post so I hope I am putting this in the correct place.
What I am trying to do is simple in theory but I have tried over and over and am having no luck in getting this to work. I wish to calculate the power in specific frequency bands for heart rate variability analysis.
Referring to the article "Using LabVIEW for Heart Rate Variability Analysis" http://zone.ni.com/devzone/cda/epd/p/id/5832 I am aware of the steps I need to follow.
I have plotted the RR intervals and resampled these with cubic spline interpolation to give a nice time dependent series. I then wire this to a PSD VI and this is where I am out of my depth.
I know from the above article that I am looking for power in these frequency bands
VLF
ms2
Power from 0–0.04 Hz.
LF
ms2
Power from 0.04–0.15 Hz.
HF
ms2
Power from 0.15–0.4 Hz.
The NI Biomedical Startup kit can do these, however I am unable to look into the source code as I do not have some required plugins in my installation. I have LabVIEW 8.6 full development system.
As this is not my area there is a steep learning curve and I have read many forum posts and pages but am still unsure of what I need to do here.
It is my understanding that the frequency resolution is simply the sample rate/number of samples. So if I require a resolution of 0.01Hz then theoretically 100Hz sample rate and 10,000samples would give me this.Furthermore I gather that the size of the output array from the PSD VI is equal to the # of data points (This i have just noticed from trial and error so I may be wrong).
Therefore if I am using the above values then is it correct that PSD would return an array and all I need to do is simply sum the contents of those array elements to get the power?
For example if frequency resolution is 0.01 , then to get power from 0-0.04Hz I must simply add the first 4 elements in the PSD output array?
I have made a test VI to show what I am talking about and attached it to this post.
Some feedback on the required approach would be a lifesaver here. I have purchased a couple of books and read through pages of forum posts but am still having trouble with this.
Many thanks!
Attachments:
labviewhelp.jpg ‏53 KB

Sorry about that, I didn't realize you wanted to run the code too The VI was doing a bunch of other stuff so I have tried to clean that out and just leave the relevant bit. As mentioned above, the case block executes when a peak is detected in the data and appends this value to an array.
I am using the technique of resampling the data because this is what was mentioned in this http://zone.ni.com/devzone/cda/epd/p/id/5832 and also in another reference that I have been following titled "Heart Rate Variability Standards of Measurement, Physiological Interpretation, and Clinical Use" http://circ.ahajournals.org/cgi/content/full/93/5/1043 which states
"The spectrum of the HRV signal is generally calculated eitherfrom the RR interval tachogram (RR durations versus number ofprogressive beats; see Fig 5a,b) or by interpolating the DES,thus obtaining a continuous signal as a function of time, orby calculating the spectrum of the counts–unitary pulsesas a function of time corresponding to each recognized QRS complex.35Such a choice may have implications on the morphology, themeasurement units of the spectra, and the measurement of therelevant spectral parameters. To standardize the methods used,the use of RR interval tachogram with the parametric method,or the use of the regularly sampled interpolation of DES withthe nonparametric method may be suggested; nevertheless, regularlysampled interpolation of DES is also suitable for parametricmethods. The sampling frequency of interpolation of DES mustbe sufficiently high that the Nyquist frequency of the spectrumis not within the frequency range of interest."
Attachments:
Exp-PulseOximeter.vi ‏205 KB

Any equalizer program in LabVIEW SVT which can control the dBPa under 1/3 octave frequency band?

Could we adjust the dBPa of a wav file by equalizer and then save the dBPa modified file to the other wav file for play? The equalizer should be controlled under 1/3 octave frequency band.

Taipo,
If you import the .wav file into LabVIEW and convert it to the waveform data type, you could use the SVT to do third-octave analysis on the waveform and then use the SVT Weighting Filter VI to adjust the level of different octaves in the signal.
If you are looking for a pre-made equalizer example for a .wav file in LabVIEW, we do not have an example that does that at this time. However, there are many programs available on the internet that can equalize a .wav file.
Sincerely,
Ross C
Applications Engineer
National Instruments

Generation of test limit masks for frequency response (limit testing in SAV)

Does anyone know a simple way for generating test limit masks from a saved frequency response?
The saved frequency response is from a reference measurement, and I need the limits to follow this response. I must be able to punch in different dB values for upper and lower limit, and for different frequency bands.
Thanks
Truls

Ciao emmanuele,
I think what you are searching for is the Extract Single Tone Information.vi that you can find under Waveform-->Analog Wfm-->Measurements-->Extract Tone.
Have you already taken a look?
Antonios

Analysis of the microphone signal-frequency band

Hi
I made a program to analyze the signal from the microphone (FFT, STFT) but I have one thing to do. I have a graph amplitude-time
I need to change the signal frequency for example 50 Hz for example by moving the slider that on the chart were waveforms amplitudes in certain frequency bands.
How to choose the frequency of the signal to change the band on the graph?
Thank for help.

In your analysis results, what is the delta frequency between datapoints? Just increment through the array of amplitude values. For example, if your datapoints are 5Hz apart, simply index out every 10th value in the amplitudes. If the increment is a non-integer value, you will need to do some interpolation, but other than that the process is basically the same.
Mike...
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

Octave analysis of frequency domain data in SVT

Hello!
How can I make the octave analysis of frequency domain data in Sound & Vibration Toolkit?
Thanks,
Alfrednovi

Hi!
To make the octave analysis of frequency domain data you have to pass in your time domain data to the Octave Analysis VIs. The time domain data will allow you to window the signal using the correct values.
The Sound and Vibration toolkit has several examples that show how to do this. You can find them under Help>>Find Examples and then browsing to Toolkits and Modules>>Sound and Vibration. This directory has Traditional DAQ and NI-DAQmx examples as well as Octave and Third Octave analysis.
You can also look for other examples using the Example Code Library.
Good Luck,
Tica

Third octave analysis of a blast signal

Hi,
I am trying to analyze one blast signal in third octave band. I am taking a narrow band power spectra of the signal and it is giving me the correct values, but when I am trying to do third octave band power spectra it is not giving me the correct results. I tried using the SVT octave analysis from sound and vibrations toolkit but still it is not giving me right results.
The sampling frequency is 24000Hz.
I am attaching the Vi and the file which I am trying to analyze. I am trying to solve this problem from 4-5 hours and still not able to solve this. Any kind of help will be highly appreciated.
Thanks,
Nitin
Attachments:
Power spectra and third octave.zip ‏1225 KB

Hi again,
I figured that problem out. but still I am not getting the values from 10 Hz, even when I am setting the low band frequency to 10 Hz. It is giving me the value from 20 Hz. I am attaching the new VI and the file.
Thanks,
Nitin
Attachments:
Power spectra and third octave.zip ‏3388 KB

Fractional Octave Analysis

My current application reads from six microphones in a reverb room, averages the signals and reports the data as a single source. In the interest of tonal diagnostics we would like to be able to record data in full and 1/3 octaves at the same time. Since I could not find a single vi in the sound and vibration tool-kit that does this I wrote a quick program that processes the same signal through the SVT Fractional-octave Analysis.vi, one defaulted to read full octave and the other is user selectable but will generally be used to read 1/3 octave. My issue occurs when I go to check the accuracy of the readings, it is my understanding that the log sum of the bands for the 1/3 octave for example should equal the value given for the frequency in the full octave band. So if i look at 50, 63, and 80 in the 1/3 octave band their sum should be the value given at 63 for full octave band. I'm using the equation Lp = 10*log(10^(L1/10)+10^(L2/10).......+10^(Ln/10)). A set of readings I've taken looks like this:
Full Octave
63 - 43.6
1/3 Octave
50 - 37.3
63 - 37.3
80 - 39.4
Lp = 10*log(10^(37.3/10)+10^(37.3/10)+10^(39.4/10))
Lp = 42.9
My calculated value of 42.9 and read value of 43.6 are close but I don't understand why the discrepancy is even there if its off the same signal. Any suggestions? I know this is a fairly long post, thanks in advance.
LabVIEW 2012 - Windows 7
CLAD

Hi MeCoOp,
The reason for these discrepancies is because of how octave analysis is implemented. Doing a straight sum of the bins assumes a brick wall filter between the different bands whereas in actuality these filters have skirts. These skirts overlap and to sum up the powers would need to take into account these filter characteristics. Since these skirts level out over an infinite bandwidth, you'll see that the power amongst the whole signal is the same when calculated as either full octave or 1/3 octave.
For more information regarding Octave Analysis and the ANSI/IEC standards, please look at this link.
http://zone.ni.com/devzone/cda/tut/p/id/101
PBear
NI RF

How to perform power spectra analysis in DIAdem

Dear all:
I am a beginner in DIAdem but I have to complete my PhD thesis that is about the
analysis of rat EEG in DIAdem. I have acquired 10G data of rat EEG. I prefer the
power spectra method. Would someone please tell me:
1. How to perform power spectra analysis of multichannel EEG(8 channels) in
DIAdem? I hope the unit of the vertical axis is microV^2, but not dB ,nor
10*log10(microV^2/Hz).
2. How to calculate the absolute power and the relative power of EEG at a certain
frequency band in DIAdem? Is it possible to do it in DIAdem?
Thank you very much
Jing
[email protected]

Hello,
It looks like you posted this question on a different thread. Please refer to this thread Duplicate Post for information about your question.
Regards,
Kevin L.
Applications Engineer
National Instruments

How to make third-octave analysis program?

"I want to make a program which can do Third-Octave Analysis. But I haven't any DAQ device of NI company. I use a DAQ device of Nicolet company. That device can tranfer the acquired data as a file to a computer, and then I can use a software to transform the data into ASCII format. The DAQ device hasn't an anti-alias filter. How can I make the program with LabView? My version of LabView is 5.1."

The task that you are inquiring about could become quite complicated. for
example, if you are performing acoustical analysis then frequency and power
become your primary points of interest. However if you are performing
analysis of shock and vibration then additional processing will be required.
I would recommend that we take this off of the news group and work direct.
I can be reached @ [email protected]
remove no_spam_ for real address
Mike
"stewart342" wrote in message
news:[email protected]..
> The DAQ device of nicolet is called 'vision'. What I mean is how can I
> make a VI to get the analysis result from the data acquired. Because I
> am not good at LabView and signal
processing thoery, I hope you can
> give me a brief example. Though the device provides a filter, the
> cutoff frequency is not arbitrary. So another question is: If I don't
> use an analog anti-alias filter, can I use a digital filter instead?
> The raw data I've got is in ASCII format. The first column is the
> time, and the following columns are the signals acquired from each
> channel. Supposed the data haven't been filtered by the anti-alias
> filter.

Is there a roll-off with the SVT octave analysis vi's?

I built a spectrum analyzer that displays 1/3 octave and narrowband data. I'm using the PXi chassis with 3 NI4472 daq cards. I noticed when putting in low frequency tonals (from function generator, amplified to 1 Vrms) the SVT 1/3 octave analysis vi has a roll-off associated between 10-100Hz. Narrowband (using power spectrum vi) quantifies the correct level extactly. I've noticed the SVT Octave analysis vi's roll-off the amplitude levels by as much as 50-60dB at 10 Hz. Does anyone know the solution to this problem.

Could you post a sample of the code that demonstrates the issue? Are you applying weighting (A-weighting would apply a relative response of -70 dB at 10 Hz) to the signal when you do octave analysis?
When I input a 10 Hz tone from a function generator to to AI0 of a 4472, I get consistent results between the power spectrum and 1/n octave (see attached results).
Another thought, how did you implement 1/3 octave analysis? The 1/3 octave analysis VIs take an enum for the low frequency where the lowest frequency in the enum is 20 Hz. I had to use the 1/n octave VI which takes a DBL for the start frequency.
Hopefully, some of this rambling helps,
Doug
Doug
NI Sound and Vibration
Attachments:
Power_Spectrum_vs_1_3_Octave_with_4472.vi ‏67 KB

Frequency response function modal analysis

After reviewing the signal analysis functions in DIAdem I have realized them to be a bit limited for modal analysis. I have a couple hammer impact tests that I need to process a frequency response function for, and since this is brand new to me I'm not seeing anything in the embedded function list that is going to help me. I was wondering if anyone out there has a couple of pointers on generating a FRF plot for modal hammer impact tests. I did notice that the ChnFFT2 command allows me to generate a transfer function, coherance, and FFT Cross Spectrum channels for analysis. Though I might be confused and this may be everything I need. My FFT2 settings are below.
[code]
FFTIndexChn      = 0
FFTIntervUser    = "NumberStartOverl"
FFTIntervPara(1) = 1
FFTIntervPara(2) = 2500
FFTIntervPara(3) = 1
FFTIntervOverl   = 0
FFTNoV           = 0
FFTWndFct        = "Rectangle"
FFTWndPara       = 10
FFTWndChn        = "[1]/Time axis"
FFTWndCorrectTyp = "No"
FFTAverageType   = "No"
FFTAmplFirst     = "Amplitude"
FFTAmpl          = 1
FFTAmplType      = "PSD"
FFTCrossSpectr   = 1
FFTCoherence     = 1
FFTTransFctType = "Spectrum H0"
FFTCrossPhase    = 0
FFTTransPhase    = 0
Call ChnFFT2("[1]/Time axis","'[1]/H_1' - '[1]/H_4'","'[1]/A_1' - '[1]/A_4'") '... XW,ChnNoStr1,ChnNoStr2
[/code]

Standard modal analysis has something denoted as FRF. I have a labview application note "The Fundamentals of FFT-Based Signal Analysis..."
Frequency Response Function
The frequency response function (FRF) gives the gain and phase versus frequency of a network and is typically computed as
where A is the stimulus signal and B is the response signal.
The frequency response function is in two-sided complex form. To convert to the frequency response gain (magnitude) and the frequency response phase, use the Rectangular-To-Polar conversion function. To convert to single-sided form, simply discard the second half of the array.
You may want to take several frequency response function readings and then average them. To do so, average the cross power spectrum, SAB(f), by summing it in the complex form then dividing by the number of averages, before converting it to magnitude and phase, and so forth. The power spectrum, SAA(f), is already in real form and is averaged normally.
Refer to the Frequency Response and Network Analysis topic in the LabVIEW Help (linked below) for the most updated information about the frequency response function.
http://zone.ni.com/devzone/cda/tut/p/id/4278
So the options for FFT2 are
No
DIAdem does not calculate a transfer frequency response.
Spectrum H0
DIAdem calculates the transfer frequency response by dividing the FFT of the output signal (A) by the input signal (E): FFT(A)/FFT(E). DIAdem averages the amplitudes of the individual transfer functions.
Spectrum H1
DIAdem specifies the cross spectrum and the auto spectrum for each signal pair. DIAdem calculates the transfer frequency response by dividing the averaged spectra: Middle(cross(A,E))/middle(auto(E)). DIAdem does not average phases, because phases can delete each other.
Spectrum H2
DIAdem specifies the cross spectrum and the auto spectrum for each signal pair. DIAdem calculates the transfer frequency response by dividing the averaged spectra: Middle(auto(A))/middle(cross(E,A))
If you assign the values Spectrum H1 or Spectrum H2 to the variable FFTTransFctType, DIAdem averages and divides the cross spectra and the auto spectra and calculates the amplitudes last.
Which state auto spectrum when FRF is power spectrum.

Power BI analysis services connector - the remote server returned an error (403)

Hi all, does any one have any suggestions what to try to identify the configuration problem I have?
I have, a SSAS 2012 tabular instance with SP2, there is a database on the instance with a read role with everyone assigned permissions.
When configuring the Power BI analysis services connector, at the point where you enter Friendly Name, Description and Friendly error message, when you click next I receive the error "The remote server returned an error (403)."
I've tested connecting to the database from Excel on a desktop and connect fine.
I don't use a "onmicrosoft" account so don't have that problem to deal with.
We use Power BI Pro with our Office 365. As far as I can tell that part is working ok as I pass that stage of the configuration with a message saying connected to Power BI.
The connector is installed on the same server as tabular services, its a Win2012 Standard server. The tabular instance is running a domain account that is the admin account for the instance (this is a dev environment) that account is what I've used in the
connector configuration. It's also a local admin account. There is no gateway installed on the server.
Any help would be greatly appreciated, thanks, Brian
Brian Searle

Brian-
One other common issue I've seen is the UPN not quite matching. Log onto the SSAS server as the user who's logged into Power BI. Then open a command prompt and run:
whoami /upn
Hopefully the UPN it says will match your EffectiveUserName test and will match exactly how you're signing into the Power BI site.
If that doesn't work, your best bet is to go to
http://support.powerbi.com/ and click Contact Support and describe this situation and someone from the Power BI support team should get in touch with you to troubleshoot.
http://artisconsulting.com/Blogs/GregGalloway

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

Question about octave analysis

Hello !
I have the following question about the octave analysis vi's.
When the single octave analysis is made, shouldn't there be 3 bands below 100 Hz ?
According to the octave analysis subvi, the bands should be located at 16, 31.5 and 64 Hz.
I've tryed to make a comparison between octave, 1/3 octave and 1/24 octave.
It seems there is no difference.
I'm running LabView 8.5.1 with SVT 6.0 on windows 7 professional.
This is not happening. See the attached vi for an example of the problem.
P.S. : The file Engine runup is a sample. please rename extension to WAW.
Thank you.
Attachments:
Engine Runup (mic).wav.jpg ‏235 KB
Sonometru.vi ‏330 KB

I also have problems with octave analysis, I'm making the acquisition of a pink noise from my audio card and checking the response curve through an analysis of octaves, to obtain a flat response curve, I need to set a number of samples of at least 88200, but this way I can not get a high-speed acquisition, only about one aquisition/second, putting a value of 2000 samples the speed is adequate, but the response curve in octaves loses response below 1000 Hz gradually until around 20 Hz is practically nil, I need help please.
best regards.

Limit testing on frequency/band power (octave analysis) data

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