The switching from the carrier to the NS is performed
on the HP channel only, correct? Just want to make
sure I am not missing anything.
Is the 12 kHz cut-off based on designs you have seen
or is based on linguist analysis? IOW, how arbitrary
is that point?
--Shemp
> One easy way to extract voiced/unvoiced information
> (as I recall) is
> to use a high-pass filter with a cutoff at 12 kHz or
> so. Plosive and
> fricative sounds have more energy in the higher
> regions of the
> spectrum, so when an S or F or P or whatever is
> spoken, the HP filter
> passes the high spectra which is rectified and used
> to trip a Schmidt
> trigger (threshold detector). This is used to
> control an electronic
> switch, which switches from the default carrier to a
> noise source.
> As soon as the unvoiced sound is over, the switch
> reverts back.
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