Microfreak/UG/19 Appendix B Vocoder/02 How It Works

• 19.2. How Does Vocoder Work?

  • The MicroFreak analyzes incoming sound with 16 tuned bandpass filters. As with the MicroFreak's own filter in BPF mode, each band emphasizes a limited range of frequencies.
  • An envelope follower tracks the loudness in each band. The resulting signals control matching filters on the carrier, allowing each formant peak to follow its own changing volume. The vocoder also recreates the overall loudness pattern at the end of the signal path.
  • MicroFreak Vocoder signal path
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  • Microfreak/UG/19 Appendix B Vocoder/02 How It Works/01 Resolution

    • 19.2.1. Resolution

      • Early vocoders used roughly 10 frequency bands, which could make speech sound indistinct. The MicroFreak uses 16 bands to recreate the voice more accurately.
  • Microfreak/UG/19 Appendix B Vocoder/02 How It Works/02 Voice

    • 19.2.2. The Perfect Modulator: Your Voice

      • A useful vocoder sound depends on pairing the modulator with a suitable carrier. Speak or sing with clear, even exaggerated articulation to drive the analysis filters.
      • Plosives such as “p,” “t,” and “b,” and sibilants such as “s,” “ch,” and “z,” can confuse the filter banks. The vocoder's high-pass filter helps remove them. Its hiss function can add high-frequency energy to help the filters respond.
  • Microfreak/UG/19 Appendix B Vocoder/02 How It Works/03 Vocoder Osc

    • 19.2.3. The Vocoder Oscillator

      • A carrier rich in overtones gives the vocoder more material to shape. Use the Wave knob to move through sawtooth, pulse width, and noise waves; see also Microfreak/UG/06 Dig Osc/03 Types/22 Vocoder.
      • The Digital Oscillator
        • 
      • Wave positions
        • 0%: sawtooth.
        • Around 11%: pulse wave at 50% duty cycle.
        • From 11% to 90%: increasing pulse width, reaching 97% duty cycle.
        • 91–100%: noise.

      • Note/Info The manual gives different duty cycles at Wave 90%: 97% here and 99% in Microfreak/UG/06 Dig Osc/03 Types/22 Vocoder.
        

      • Sawtooth, pulse-width, and noise waveforms
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      • Timbre and Shape also control the Vocoder Oscillator.

      • Note/Info Oscillator Type cannot be modulated while the Vocoder Oscillator is active.
        

      • Microfreak/UG/19 Appendix B Vocoder/02 How It Works/03 Vocoder Osc/01 Timbre

        • 19.2.3.1. Timbre Encoder

          • Timbre selects the frequency range used for analysis and resynthesis. Vowel formants peak at different frequencies: for example, a “u” may have peaks near 330 and 1260 Hz, with variation across voices.
          • Matching the range to the speaker, or to an instrument used as a modulator, helps the filters respond to the frequencies that matter. Monitoring fewer frequencies can improve response time and output.
          • Vocoder filter bands and frequency response
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      • Microfreak/UG/19 Appendix B Vocoder/02 How It Works/03 Vocoder Osc/02 Shape

        • 19.2.3.2. Shape Encoder

          • Shape sets the bandwidth of each bandpass filter. Higher settings narrow the filters' frequency response and produce more pronounced harmonics.