I am inputting my guitar tunes(.wav files) and I am trying... 
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 I am inputting my guitar tunes(.wav files) and I am trying...

I am inputting my guitar tunes(.wav files) and I am trying to do an
FFT on this. Wen I do, the FFT signals are very small and are not on
the right frequency scale. However I am able to simulate a sine wave
and get an accurate FFT plotted as a cluster.
My .wav file has about 8100 samples and has a sample rate of 11050.

I pass the samples into FFT. The output I devide by the size of the
array(8100??). This I seperate into 'real' and 'polar'. The 'real' I
use to plot. My plot has a starting value of '0' on the X axis. My
problem is with the other value for the cluster, i.e; To plot this I
need 1. 'real' part of the FFT output. 2. the 'x' axis starting
value(0) and 3. how do i get this value? I tried deviding the sampling
rate by the size of the samples, but the FFT plot is really wrong.
Anybody has an example vi to convert .wav files to FFT? Thanks alot!!!



Mon, 08 Sep 2003 04:10:40 GMT  
 I am inputting my guitar tunes(.wav files) and I am trying...
Open the VI called labview\examples\measure\maxmpl.llb\power spectrum
example.vi.  Then, delete the portion which simulates the data for the
FFT.  In its place, put the Graphics & Sound\Sound\Sound File\Snd Read
Wave File.VI.  Select the wave to get.  If it is a stereo wave file,
an array of points is output from this VI.  Strip off one channel, and
input that into a Build Waveform, along with a t0 of 0 and a delta T
of 1/11050.

If you run the VI, it should perform the way you are wanting.

Mark



Mon, 08 Sep 2003 22:56:11 GMT  
 I am inputting my guitar tunes(.wav files) and I am trying...
Mark! Thanks for the reply. However I am unable to find that example
you mentioned. I am using Labvew5.1. In the examples I see:
Labview/examples/analysis/measure/measxmpl.llb. This has 'amp spectrum
analyzer", "dynamic sig analyzer" and "simple spectrum analyzer".
Is this the LLB you refered to? And none of these show an "FFT" vi,
but do show digrams with Power/spectrum analyzers. Thanks alot!!!


Tue, 09 Sep 2003 01:10:05 GMT  
 I am inputting my guitar tunes(.wav files) and I am trying...
Okay, I was using LV6i.  In LV5.1, there's a VI called
labview\examples\daq\solution\benchtop.llb\benchtop spectrum
analyzer.vi.  If you look at the diagram, there is a vi that is in the
Acquire, Process and Average loop.  If you look at that VI's diagram,
remove the portion that gets the data from the data acquisition card.
(You'll get it from your file.)

Replace that the same way I explained before, except for the part that
says to put it into the "build waveform" part.  That only exists in
LV6i.

Mark



Tue, 09 Sep 2003 01:52:20 GMT  
 I am inputting my guitar tunes(.wav files) and I am trying...
Well, I noticed a couple of things.  First, you need to strip off the
last part of your FFT array before displaying it to the graph, because
you can only effectively see frequencies to 1/2 your scan rate, or
11025 Hz.  Second, you used the wrong VI to get the real portion of
your FFT--you chose the "complex to polar", when you really wanted
"complex to Re/Im".  Try that, and your results will be different.
Also, for future reference, you may want to "window" your time array
with a Hanning or Hamming window to smooth transition points.  LabVIEW
has a whole article devoted to these concepts in the help menu.

Mark



Tue, 09 Sep 2003 23:57:33 GMT  
 
 [ 5 post ] 

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