[music-dsp] Detecting notes in samples

Axel Nackaerts Axel.Nackaerts at esat.kuleuven.ac.be
Mon Dec 11 09:36:38 EST 2000


Arlen Barr wrote:

> "Sergio R. Caprile" wrote:
>
> >not much to add here.  There are several methods to determine the pitch for
> >non-realtime applications.  I have a master's thesis here (unfortunately in
> >Dutch) that goes over the methods.  These are (I selected the best ones)
> >
> >* lowest peak in fft
> >* highest peak in fft
> >* peak with most harmonics
> >* frequency that matches as a fundamental with most of the other peaks
> (Xavier
> >Serra's method, note that this doen't mean that this frequency really
> appears in
> >the signal)
>
> In what case(s) would the actual fundamental be missing?  Unless it falls
> outside of the bandwidth of the recording ...

What we (perceptually) hear has the pitch could be a "missing" frequency.  Say,
you have the series:

220 Hz, 440 Hz, 660 Hz, 880 Hz, 1100 Hz etc.

We hear this as a low A.  Now reduce the amplitude of the 220Hz partial -> we
still hear this as a low A.  At a certain point, the amplitude is zeros and we
still "hear" it.    The problem is that if we take 440 Hz as the fundamental,
we expect the series 440 Hz, 880 Hz, 1540 Hz etc. so something is wrong.
Example: a guitar played very near the bridge as almost no 'real" fundamental
but the perceived pitch stays the same.

There are a few examples of this effect on the web - I don't have a link at
hand but it's not difficult to find.

regards,

Axel Nackaerts

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