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identifying fundamental frequency

Started by sfol...@iupui.edu June 20, 2007
Hello,

I am working on a project that I am taking a single string vibration from an electric guitar coil pick-up and modifying the signal through a 56311 Motorola (Freescale) DSP. Right now, I am running into the roadblock of finding an algorithm that will identify the fundamental frequency of the note that is being plucked. After identifying the fundamental, I will be modifying the signal to reproduce the sound of other instruments.

Any help or information is greatly appreciated.

Thankyou,

Sean Foley
Hi Sean,

the regular algorithm to determine discrete frequencies in a spectrum is the Fourier Analysis. For discrete time signal processing this transform is modified to the Discrete Fourier Transform implemented as FFT (fast Fourier Transform). Fortunately there are application codes available for the DSP56311.

Look at: http://www.harmony-central.com/pv_obj_cache/pv_obj_id_BA98BE9D0A153AC922D1FC6E1775F1D66BB71100

for the Freescale application note (this also gives some background on the theory behind) since it cannot be found at the Freescale website anymore. They have cleaned up their website and deleted lots of old, but important stuff unfortunately.

You can find a lot of this deleted things including all 56311 doc and assembler source code for FFT at:

http://home.agh.edu.pl/~rumian/DSP_stuff/56300/

The FFT transforms your signal to the individual spectral components. You may determine the lowest frequency then. This is the common way to do spectral analysis.

An alternative way would be to use Discrete Wavelet Transform but this requires a significant deeper insight to the theory and to develop your own DSP application code.

Hope this helps

Christian

> Hello,
>
> I am working on a project that I am taking a single string vibration from
> an electric guitar coil pick-up and modifying the signal through a 56311
> Motorola (Freescale) DSP. Right now, I am running into the roadblock of
> finding an algorithm that will identify the fundamental frequency of the note
> that is being plucked. After identifying the fundamental, I will be
> modifying the signal to reproduce the sound of other instruments.
>
> Any help or information is greatly appreciated.
>
> Thankyou,
>
> Sean Foley