Sign Overview
Voice biomarker signs are the acoustic analysis units that underlie both the Model API and the Sign API. Submit audio via POST /v2/models/{model_name}/analyze to run a named bundle of signs together, or via POST /v2/signs/{sign_name}/analyze to analyze a single sign individually. Each sign targets a specific condition or health state by measuring how that condition alters the mechanics of speech production — breath support, laryngeal control, articulation timing, and prosodic patterning. Every sign carries an evidence tier that reflects the depth of published academic and scientific research behind that voice biomarker.
The acoustic indicators listed for each sign in the full reference are interpretable speech features associated in the literature as vocal mechanisms linked to that condition. They are provided for informational purposes and represent the research basis for each sign — not a description of how every individual recording is evaluated. Sign outputs reflect a broad acoustic analysis; no single indicator solely determines a result.
Named Models (Model API)
Submit audio to POST /v2/models/{model_name}/analyze using one of these eight named model bundles. Each bundle runs a set of signs and returns summary + signals[] + audio_quality. See Model API for request shape, response fields, and examples.
Discover available models and their sign composition with GET /v2/models or GET /v2/models/{model_name}.
Evidence Tiers
Use tiers to inform routing logic, display decisions, and clinical workflow design. The table below summarizes tier requirements and recommended deployment contexts.
| Tier | Requirements | Recommended for |
|---|---|---|
| Established | Three or more peer-reviewed studies; findings replicated across two or more independent research groups; at least one prospective or large-scale validation | Workflows and products where you want the strongest published evidence base for the voice-based signal |
| Emerging | Published peer-reviewed evidence; replication present but not yet at clinical-validation scale; active research pipeline | Research partnerships, pilots, and validation studies where newer voice-specific literature is appropriate |
| Investigational | Acoustically plausible mechanism with supporting physiological rationale; no peer-reviewed voice-specific detection study published | Exploratory research, hypothesis generation, supplementary data streams |
Speech Features
Each recording is analyzed using thousands of acoustic speech features that capture how the voice and speech behave — spanning timing, energy, spectral content, and vocal quality. In addition to the signal scores, wellness metrics, and extended metrics returned per model job, the API exposes a subset of interpretable speech features for additional use and understanding of the analyzed speech signal. These features are provided to give transparency into the acoustic dimensions being measured; they represent a human-readable window into a much broader feature space driving the models.
| Feature ID | Label | Unit | Description |
|---|---|---|---|
| pitch_mean | Average Pitch | Hz | The average highness or lowness of the voice |
| pitch_variability | Pitch Variability | ratio | How much the pitch fluctuates — monotone vs. expressive |
| loudness_mean | Average Loudness | dB | The average equivalent sound level in decibels |
| loudness_variability | Loudness Variability | ratio | How much the loudness changes over time — dynamic range |
| speech_rate | Speech Rate | syllables/s | Speed of speech including pauses, in syllables per second |
| articulation_rate | Articulation Rate | syllables/s | Speed of speech excluding pauses — how fast words are actually spoken |
| pause_duration_mean | Average Pause Duration | s | How long the average silence or pause lasts between words |
| voice_jitter | Voice Roughness (Jitter) | % | Micro-fluctuations in pitch. High values sound raspy, gravelly, or creaky |
| voice_shimmer | Voice Shimmer | dB | Micro-fluctuations in volume. High shimmer can sound breathy or unstable |
| voice_clarity_hnr | Voice Clarity (HNR) | dB | Harmonic-to-Noise Ratio. Higher values mean a clearer, less noisy voice |
| voice_breathiness | Voice Breathiness | dB | A measure of breathiness. Higher values indicate a breathier voice |
See Signs reference: Established, Emerging, and Investigational.