[sdiy] Has anyone built a voice pitch tracker?

Tue Nov 12 20:22:00 CET 2002

I've tried this electronotes circuit as well.

The reason it does not work on guitar is because the (very real) stiffness of the strings makes the harmonics sharp... the beating
means that eventually, there will be a point where the primary and
secondary peaks are equal.

Voice is different... The harmonic content cannot be predicted
accurately.

The usual technique is to use a lowpass filter, over the two octave
range it might work (only 24dB-48dB loss)... but it will add phase shift...

Then the harmonic "should" be less in amplitude... you hope wish pray.

H^) harry

>Dan wrote:
>> 1. I need to eliminate the second harmonic - and when I sing very low 
>> the second harmonic is within the range of interest, so it can´t be 
>> filtered out with conventional filters.
>Ah, the joys of pitch extraction.  I've had exactly the same issue (I 
>think) when trying to extract pitch from an electric guitar signal.
>While I don't have a specific answer for you, in Electronotes # 53 
>Bernie Hutchins covers a technique which might be worth experimenting with.
>It basically involves using a peak detector type envelope follower to 
>generate a DC voltage that tracks the peaks of the original waveform. 
>The time constant of this should be adjusted so it doesn't miss too many 
>peaks (it will have lots of ripple but I think that's ok).
>Then take this envelope (properly scaled), and use it as a reference to 
>a comparator of which the original signal is the input.  The idea is to 
>trigger the comparator on the fundamental peaks and not the second 
>harmonic peaks.  In a working situation, the output should be a pulse 
>train at fundamental frequency.
>This technique falls apart when the second harmonic is as big as the 
>fundamental (this happened in my guitar example and pre-filtering plus 
>some other jumping through of hoops helped).
>I'm not sure if that helps you get where you're going but I thought I'd 
>throw it out there.  I'd be happy to copy the article for you.  Let us 
>know what you come up with!
>Buck