Vocoder design

[jorgen.bergfors at idg.se]

Hi Scott, thanks for the formulas. I'll try to enter them in Excel.
Last night I did some PCB layout. It seems quite possible to fit eight channels on one 100x160 mm board. That would make it 2 1/2 boards for the entire vocoder.
One thing missing in the vocoder is a voiced/unvoiced detector. Any of you gurus have any idea how one would work?
I would imagine that the circuit would crossfade in a certain amount of noise, when the detector exceeds a certain threshold.
The noise would go through the filter bank too, of course. You could also patch another signal instead of the white noise, if you wanted.
I think a circuit like this would add really interesting possibilities. The question is how the detector would operate.
How could you determine if the signal is pitched or unpitced? Maybe it could be considered unpitched if several adjacent bands are "on"? But I doubt that it would work in all situations.
Let's hear some better ideas!

/Jorgen