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Old 03-16-2006, 01:48 PM   #1
Registered: Apr 2004
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compute audio signals

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
Old 03-17-2006, 10:58 PM   #2
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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
Registered: May 2004
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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
Registered: Apr 2004
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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 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
Registered: May 2004
Posts: 552

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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".

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
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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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