Antwort: [sdiy] Has anyone built a voice pitch tracker?

[Ingo Debus]

Christian.Bergmiller at daimlerchrysler.com wrote:
> Hello,
> 
> 
> how do this cheap guitar(or instrumen)t tuners work?
> they extract the pitch of complex waveforms really good.
> (the most of them cheap ones are slow but in some applications this may be ok)
> 
> are they all dsp based?

Don't know if today's guitar tuners are dsp based, but the early 
analog ones don't really extract the pitch, but compare the frequency 
of the input signal to a reference frequency. The input signal is 
squared and set to a fixed pulsewidth with a monoflop. The pulsewidth
and amplitude of the reference signal is the same. Both signals are 
subtracted and averaged. When the output is zero volts, the 
frequencies are same. Simple and accurate.

Ingo