> ## Documentation Index
> Fetch the complete documentation index at: https://docs.medera.info/llms.txt
> Use this file to discover all available pages before exploring further.

# Voice Quality

> Jitter, shimmer, and HNR

Voice quality features are computed by `_extract_voice_quality(sound)` using Praat point-process analysis.

| Feature                    | Unit | Normal range |
| :------------------------- | :--- | :----------- |
| `jitter`                   | %    | \< 1.04 %    |
| `shimmer`                  | %    | \< 3.81 %    |
| `hnr`                      | dB   | > 20 dB      |
| `voice_quality_confidence` | 0–1  |              |

Elevated jitter and shimmer correlate with vocal effort, fatigue, and emotional distress. Decreased HNR signals breathiness or hoarseness.