Methodology

How Podonos rates your voice models

How automated MOS scoring works and what it measures

A learned panel simulation

Podonos builds a neural scoring model from thousands of (audio, MOS score) pairs gathered in real listening studies. During inference, it estimates the rating a listener panel would give without convening one. Rather than rules, it learns an approximation of human perceptual judgment.

Three independent scoring dimensions

Naturalness

Checks whether the voice sounds human, covering fluency and human-likeness.

Prosody

Checks whether rhythm, stress, and intonation fit the text, flagging robotic pacing.

Pronunciation

Checks word accuracy and catches phoneme errors common in under-trained TTS.

Calibration

Calibrated with human listener panels

We gathered MOS ratings from listener panels covering multiple TTS systems in our internal beta. The model is recalibrated quarterly as listener data grows. Current calibration: R-squared > 0.89 against 2,400 listener ratings, internal beta, Q4 2024.

R² 0.89
Correlation
R-squared > 0.89, 2,400 human ratings, int. beta Q4 2024
Quarterly
Recalibration cadence
Listener data arrives continuously; the model updates quarterly.
Multi-system
Training coverage
Panels assess varied open-source and commercial TTS outputs.

One endpoint, all results

Send an audio URL or binary to /v1/evaluate. Get JSON with mos_score, confidence_low, confidence_high, and sub_scores for each dimension. Only an API key is needed.

Request
import podonos
import os

client = podonos.Client(
  api_key=os.getenv(
    'PODONOS_API_KEY'
  )
)

result = client.evaluate(
  audio_url='https://example.com/audio/sample.wav'
)
Response
{
  "mos_score": 4.2,
  "confidence_low": 3.9,
  "confidence_high": 4.5,
  "sub_scores": {
    "naturalness": 0.88,
    "prosody": 0.79,
    "pronunciation": 0.91
  },
  "eval_ms": 1820
}

Common queries

WAV, MP3, FLAC, OGG. Up to 50MB. Stereo is downmixed to mono before scoring.
Audio stays in memory and is not saved. Your history retains only the score and metadata.
Human panels remain the gold standard. Podonos supports frequent feedback when panel cost and delay are prohibitive. For release decisions, verify results with human listeners.
We validated Coqui TTS and StyleTTS2 open-source outputs, plus commercial API outputs. Model names appear on the benchmark page.