Cascade Vocal Tract Gains, g1, g2, g3, and g4

Changes in head size or other options can sometimes produce overloads in the synthesizer circuits. If this occurs, make sure that the f4 and f5 options are set to reasonable values. If the squawk remains, you can adjust several gain controls in the cascade of formant resonators of the synthesizer to attenuate the signal at critical points. These gain controls are the Gain of cascade formant resonator (g1 through g4) options. These gains can then be amplified back to desired output levels later in the synthesis.

Use the following procedure to correct an overload (typically indicated by a squawk during part of a word):

1. Synthesize the word or phrase several times to make sure the squawk occurs consistently. Use the same test word each time a change to a gain is made.

2. Determine the default values for the g1 through g4 options for the speaker that overloads.

3. Reduce the g1 option by increments of three until the squawk goes away. When the squawk goes away, note the reduction that was needed. If more than a 10 dB decrement is required, some other option has probably been changed too much. If the squawk does not go away at all, then you may need to reduce the gv option instead of the g1 option.

4. Increase the g5 option to return the output to its original level. For example, if the g1 option was reduced by 6 dB, add 6 dB to the g5 option (or to the g4 option if the g5 option is already at a maximum). If incrementing the g5 option causes the squawk to return, then decrease the g5 option slowly until the squawk goes away.

This procedure works in most cases, but using the g2 option rather than the g1 option can work better. If you can return the g1 option to its factory-preset value and reduce the g2 option instead to make the squawk go away, then the signal-to-quantization-noise level in the g1 option remains maximized. If you can eliminate the squawk by using the g3 or g4 option rather than the g2 option, more of the cascaded resonator system can be made immune to quantization noise accumulation.