AW: Vocoder Design Questions, thanks for input

Haible Juergen Juergen.Haible at nbgm.siemens.de
Mon May 4 13:06:04 CEST 1998


	>Adding broadband noise to speech below the threshold of audibility
makes it
	>intelligible. I heard a demonstration of this on a radio show, and
it
	>really does work. Of course, it was rather noisy...

Sounds as if the vocoder in question had a problem with VCA
thresholds (?). If you don't have the individual VCA CVs exactly
trimmed to zero offset, you will either have a bleedthru of a sort
of "noise gate" threshold in each band. Some manufacturers
simply do an fixed offset overcompensation to avoid bleedthru,
and tolerate the noise gate effect. Then weak harmonics will
simply be ignored, and you need a strong dynamic compression
(or maybe some added noise) to get a decent operation.
No need to mention that a carefully adjusted trimpot for each channel 
is the better solution ...

JH.






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