CreamWare Noah Vocodizer Manual page 7

Alternate Mode (Type = On)
As an alternative to the standard mode in
which the Vocodizer analyses both upper
and lower frequency ranges, you can use
a simplified detection mode in which only
the high frequencies are examined to
determine the signal characteristic
(voiced or unvoiced).
Highpass
In this mode it is sufficient only for the
high frequency content to exceed the
threshold for the signal to be identified as
unvoiced. In Alternate mode the signal is
determined to be unvoiced more
frequently than in Standard mode, and the
intelligibility in some cases improves
because, along with the consonants like
"k" and "s", some of the other overtone-
rich parts of the signal are also identified
as unvoiced.
Vocodizer
Threshold: Sets the level at which the
high frequency energy triggers the
detection circuit to identify the signal as
unvoiced.
When set to minimum, none of the
signal will be classed as unvoiced, and
the noise source will never replace the
original signal in the output. And, as you
would expect, setting this parameter to
maximum results in the entire signal
being identified as unvoiced. In this
case, the noise source replaces the
entire signal.
Hyst: Hysteresis describes the difference
in threshold values for the upper and lower
frequency ranges. At 0, the same level
criterion applies to both ranges. With
increasing hysteresis values, less energy
is required in the lower frequency range
to defeat the unvoiced detection in the
upper range. Therefore, as you increase
the hysteresis value, signals with
sibilance are less likely to be identified
as unvoiced leading to fewer replacements
of the synthesized signal with noise.
The Hyst setting applies only in Stan-
dard mode as Alternate mode
employs only a single threshold
value.
Time: Depending on the result of the V/
UV detection, the synthesis filter is fed
either with noise (unvoiced) or the
synthesized signal (voiced). However,
the change from one to the other does
not take place immediately; rather, the
signals are cross-faded. The Time
setting adjusts the duration of the cross-
fade in milliseconds. With higher values,
noise is fed into the synthesis section
more slowly after unvoiced detection.
Contents Index
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