_extract_f0_features(sound, audio) using Praat’s autocorrelation method via speech analysis library. | Feature | Unit |
| :--- | :--- |
| f0_mean | Hz |
| f0_std | Hz |
| f0_min, f0_max, f0_range | Hz |
| f0_confidence | 0–1 | Gender-aware range:
- Male: 85–180 Hz
- Female: 165–255 Hz
- Auto: 75–300 Hz Reduced
f0_rangecorrelates with prosodic flatness — a documented marker in major depressive disorder.