How can I use a DSA to get streaming audio from FFT signals using labview?

[lost in labview]

My boss wants to be able to hear what the particle beam we work with is doing. He wants me to make a labview program that takes FFT data from the DSA and shrink the frequency down into auidble range. iam not sure where to begin. Any ideas?

[omarp]

Dear Sir,

Thank You for using the Developer Exchange.

What you can do it with LabVIEW is to acquire the time domain waveform from the particle Beam calculate the FFT shift the frequency for an audible range and then rebuild the time domain signal and apply it to a Speaker.

Of course it will depend on some aspects of your signal:

1 - What is the bandwidth(frequency content) of your particle beam signal?

2 - How the information contained in the particle beam can be transformed into a voltage signal?

3 - Will you need a special transducer?

4 - Once you have the voltage signal what caracteristic of the particle beam will the voltage signal represent?

Best Regards,
Omar De Andrade
Applications Engineering - National Instruments
Computer Based Instruments Group

[MLeo]

How do you shift the frequency to a more audible range after calculating the FFT?

M.Leo

[Megan B.]

Hi M Leo,

Shifting frequencies is discussed in this post which may be helpful.  Otherwise, I am thinking that you're working with a waveform datatype in LabVIEW?  There is a VI called Get Waveform Components which will return your initial time, delta time, and then the array of values in the waveform.  You could pull out these components and then rebuild the waveform with a new delta time using the Build Waveform VI.

Hope this helps!
Megan B.
National Instruments

[MLeo]

Hey Megan,

Thanks for your help!

I tried what you suggested, however I'm having problems with my audio output.

According to the freq spectrum graph the frequency shift works, however there is no change in sound from the speaker when I adjust the rate. Any ideas on why this happening?

I am outputting the signal through the sound card and wish it to remain as close to real time as possible.

Thanks again

M.Leo

[Megan B.]

Hey MLeo,

Check out the Generate Sound.vi that ships with LabVIEW.  This VI allows you to set the frequency of the audio output and it's easy to hear the differences.  I tried between 300 and 1000 and the changes were clear.  I suspect that the frequencies you are using are too high and either the speakers can't really show the variation or our ears can't differentiate them.

To find the VI, just go to Help>>Find Examples and search for sound. 

Hope this helps!!
Megan B.
National Instruments