How is sine-wave speech generated?

• A. By random sine wave generation
• B. By using a formant tracker to detect formant frequencies and synthesize sine waves that track their centers
• C. By filtering a recorded voice through a narrow band filter
• D. By amplitude modulating a carrier signal

Answer: (B)

Sine-wave speech is created by representing speech with a small set of sine tones whose frequencies track the formant centers over time. Formants are the vocal-tract resonances that define the major spectral peaks of speech. A formant tracker identifies the instantaneous formant frequencies as speech unfolds, and then sine waves are generated at those center frequencies with time-varying amplitudes to follow the formant trajectories. This approach preserves the essential spectral structure that carries intelligibility, even though most of the fine spectral detail is removed. It’s not produced by random sine waves, nor by simply filtering a recorded voice, nor by basic amplitude modulation of a carrier—the synthesis is specifically tied to the evolving centers of the formants to reproduce the recognizable speech with minimal components.