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Old 03-16-2006, 01:48 PM   #1
bong.mau
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compute audio signals


Hi
i need to know if there is a pgm executing the following functions or similar
i captured an audio file with audacity.
i need to analize this audio file to
compute the frequency of the signal's peak
is there a such pgm or i have to use more than a pgm
i see gnuplot but i do not know if it meet the above requirements
thanks in advance
Maurizio
 
Old 03-17-2006, 10:58 PM   #2
Matir
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gnuplot merely produces graphs, it does not handle the analysis.

I am not sure what you mean by "compute the frequency of the signal's peak". Please explain in detail.
 
Old 03-17-2006, 11:23 PM   #3
randyding
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The FFT (fast Fourier transform) of a signal extracts the frequency components.
If you google for FFT you'll find tons of information.
Matlab is a program that can do this for you, though its an expensive commercial application, and it has Unix versions.
 
Old 03-18-2006, 02:05 PM   #4
bong.mau
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to explain me better

with audacity i registered an audio file containing the sound of a mechanical instruments.
if some of you has experience using an oscilloscope
a clear signal can be see like a "square wave"
or a sinusoid.
biut my signal is not so clear an the frequency is
not stable.
so i have to analyze the file with the signal with a pgm.to identify the peaks of the signals to identify the frequency of work of mechanical instrument measured.

now a question:
does the use of FFT implies a knowledge of mathematics at master degree level or there are inside the fft pgm some commands to extract the info i need ?
looking at internet i see alsa waveanalyzer
does someone experienced using FFT or waveanalyzer or some other tools to extract data from a signal (audio or not ) file ?
thanks in advance Maurizio
 
Old 03-18-2006, 02:49 PM   #5
randyding
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Yes, I'd say it takes some basic math/programming knowledge to write a FFT program. Not Master's degree since I learned how in just a university BS degree program, in fact some advanced classes in High School do such things.

In two seconds of google searching I found a windows program called cooledit
that does "Analyze audio with Spectral View and Frequency Analysis".

http://www.sonicspot.com/cooledit/cooledit.html

I've actually have used cooledit for basic frequency analysis before and it will do what you want.

Now finding a Linux program is left as an exercise for the student.
 
Old 03-18-2006, 03:43 PM   #6
jiml8
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The fft is simply a fourier transform variant that works when the number of signal samples is a power of 2. The actual algorithm is not that difficult to implement, but understanding what it is doing does involve a substantial mathematical background.

You will find programs online that will do the computation for you.
 
  


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