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Chapter 14 The EVOC 20 PS 183
Formant Filter Parameters
The Formant Filter Window
The Formant Filter window is divided into two sections by a horizontal line. The upper
half applies to the Analysis section and the lower half to the Synthesis section. Changes
made to the High/Low frequency parameters, the Bands parameter or the Formant
Stretch and Shift parameters will result in visual changes to the Formant Filter window.
This provides you with invaluable feedback on what is happening to the signal as it is
routed through the two Formant Filter banks.
High/Low Frequency
The blue bar shown just beneath the EVOC 20 PS logo is a multi-part control which is
used to determine the lowest and highest frequencies allowed to pass by the filter
section. The length of the blue bar represents the frequency range for both analysis
and synthesis. Frequencies of any audio input which fall outside these boundaries will
be cut. All filter bands are distributed evenly across the range defined by the High/Low
Frequency values.
• To adjust the Low Frequency value, simply click-hold on the silver slider to the left of
the blue bar, and drag to the right (or left). The value range is 75–750 Hz.
• To adjust the High Frequency value, simply click-hold on the silver slider to the right
of the blue bar, and drag to the left (or right). The value range is 800–8000 Hz.
• To adjust both sliders simultaneously, click on the area between the slider halves
(directly on the blue bar) and drag to the left or right.
• You can make changes to the High/Low Frequency values directly by using your
mouse as a slider on the numerical entries—270 and 7100 Hz in the diagram.
Lowest/Highest
These parameters can be found in the two small windows on either side of the
Formant Filter window. These switches determine whether the lowest and highest filter
bands act as bandpass filters (like all of the bands between them), or whether they act
as lowpass/highpass filters, respectively. Click once on them to switch between the two
curve shapes available.
• In the Bandpass setting, the frequencies below/above the lowest/highest bands are
ignored for both analysis and synthesis.
• In the Highpass (or Lowpass) setting, all frequencies below the lowest (or above the
highest) bands will be considered for analysis and synthesis.