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170 Chapter 13 Vocoder—Basics
Due to the way human beings hear, the intelligibility of speech is highly dependent on
the presence of high frequency content. To aid in keeping speech clear, it may be
worthwhile using equalization to boost or cut particular frequencies in analysis signals
before processing them with the vocoders.
If the Side Chain (analysis) signal consists of vocals or speech, a simple shelving filter
should be sufficient. It doesn’t require much processing power, and efficiently boosts
the high-mid and treble range, which is so important for speech intelligibility.
If the synthesis signal lacks treble energy, it can be generated with a distortion effect.
The overdrive plug-in is perfect for this purpose.
Avoiding Sonic Artefacts
A common problem with vocoder sounds are sudden signal interruptions (ripping,
breaking sounds) and rapidly triggered noises, during speech pauses.
Release Parameter in the Analysis Section
The Release parameter defines the speed that a given synthesis frequency band can
decrease in level, if the signal level of the respective analysis band decreases abruptly.
The sound is smoother when the band levels decrease slowly. To achieve this smoother
character, use higher Release values in the analysis section of the interface. Longer
release times result in a washy sound.
Short Attack values are no problem. They may, in fact, even be desirable when a fast
reaction to impulse signals by the vocoder is required.