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Chapter 8 EVOC 20 PolySynth 154
When you gate speech and vocals with the Noise Gate plug-in, use Threshold to dene the level
above which the gate will open, and use Hysteresis to dene a lower Threshold level below
which the gate will close. The Hysteresis value is relative to the Threshold level.
The gure above shows a Threshold setting that is well-suited for speech compression.
Unwanted triggering by low or high frequency noise is avoided by the dedicated sidechain lters
of the Noise Gate plug-in. The Hold, Release, and Hysteresis values are suitable for most vocal and
speech signals.
Tips to enhance speech intelligibility
Keep these points in mind to achieve the best possible speech intelligibility:
•
The spectra of the analysis and synthesis signals should almost completely overlap. Coupling
low male voices with synthesis signals in the treble range doesn’t work well.
•
The synthesis signal must be constantly sustained, without breaks. The incoming side-chain
signal should be played or sung legato, because breaks in the synthesis signal stop the
vocoder’s output. Alternatively, the Release parameter of the synthesis signal—not the Release
time of the Analysis section—can be set to a longer time. You can also achieve nice eects by
using a reverberation signal as a synthesis signal. Note that the two latter methods can lead to
harmonic overlaps.
•
Do not overdrive the vocoder. This can happen easily, and distortion will occur.
•
Enunciate your speech clearly if the recording is to be used as an analysis signal. Spoken words
with a relatively low pitch work better than sung vocals—even if the creation of vocoder
choirs is your goal. Pronounce consonants well, as exemplied in the rolled “R” of “We are the
Robots,” by Kraftwerk, a classic vocoder track. This exaggerated pronunciation was specically
made to cater to the vocoder.
•
You can freely set Formant parameters. Shifting, stretching, or compressing the formants has
a minimal eect on the intelligibility of speech, as does the number of frequency bands. The
reason for this is due to the human ability to dierentiate the voices of children, women, and
men, whose skulls and throats vary. Such physical dierences cause variations in the formants
that make up their voices. Human perception, or recognition, of speech is based on an analysis
of the relationships between these formants. In the EVOC 20 plug-ins, these relationships are
maintained even when extreme formant settings are used.