Soniox STT (Async) - Benchmarks & Performance - OpenTranscription

Soniox STT (Async)

Name: Soniox STT (Async)
Author: Soniox

Batch

Soniox async batch transcription — one multilingual model across 60+ languages with speaker diarization, per-word timestamps, and automatic language identification, at a low flat token-based rate.

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25 languages · benchmarked

Overall Score

73.7

Word Error Rate

8.73%

Character Error Rate

6.18%

Match Error Rate

8.39%

Word Info Lost

13.26%

Avg Latency

6.2s

Benchmarks Run

Cost vs. accuracy

overall WER · 27 models

field · 27 models

lower-left is better

Performance by category

8 categories

WER

lower is better

Medical

1.6%

Legal

3.5%

Technical

4.9%

Finance

6.3%

General

6.6%

Conversational

12.6%

Code-Switching

16.0%

Noisy Environment

21.9%

Category	WER	CER	MER	WIL	Latency	Benchmarks
Code-Switching	16.03%	9.30%	15.69%	23.29%	10.2s	2
Conversational	12.60%	6.16%	12.47%	16.56%	8.2s	2
Finance	6.32%	2.82%	6.25%	10.13%	5.1s	2
General	6.62%	5.30%	6.47%	10.89%	5.4s	18
Legal	3.52%	1.90%	3.49%	4.55%	7.6s	2
Medical	1.62%	0.83%	1.62%	2.25%	7.6s	2
Noisy Environment	21.92%	16.67%	20.02%	32.16%	5.1s	4
Technical	4.89%	2.97%	4.84%	6.33%	7.6s	2

Performance by accent

5 accents

Accent	WER	Benchmarks
African	12.31%	1
Australian	12.31%	1
Indian	19.05%	1
British	7.46%	1
American	11.32%	1

Pricing

pay per second

Rate

$0.0017

/min

Per-second billing. Bring your own provider key and pay your provider directly — a 5% routing fee applies (first 100 min/mo free).

Set up BYOK

Cost estimator

1 hour

$0.10

10 hours

$1.01

100 hours

$10.08

1,000 hours

$100.80

Billed per second of audio processed.

API & usage

POST /api/v1/transcriptions

Model ID

soniox/stt-async

Get an API key

Authenticate every request with your secret API key as a Bearer token. Issue a key from your dashboard.

Quickstart

Upload your audio, create a job with this model, then poll the job or set a webhook_url to be notified when it completes.

# 1. Request a signed upload URL
curl https://opentranscription.io/api/v1/uploads \
  -H "Authorization: Bearer $OT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "file_name": "interview.mp3", "file_size": 3456789, "mime_type": "audio/mpeg" }'
# → { "upload_url": "...", "file_path": "...", "expires_at": "..." }

# 2. Upload the audio bytes to the signed URL
curl -X PUT "$UPLOAD_URL" --upload-file interview.mp3

# 3. Create the transcription job
curl https://opentranscription.io/api/v1/transcriptions \
  -H "Authorization: Bearer $OT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "file_path": "$FILE_PATH",
    "model": "soniox/stt-async",
    "language": "en",
    "diarization": true,
    "webhook_url": "https://your-app.com/webhooks/ot"
  }'
# → we POST a signed event to your webhook_url when the job finishes — no polling required

Key parameters

file_path

string

required

Storage path returned by the upload step.

model

string

required

The model to run this job on.

language

string

ISO 639-1 language code. Omit to auto-detect.

diarization

boolean

Label speakers (A, B, …) in the output.

webhook_url

string

HTTPS URL notified with the result when the job completes. Delivered events are signed (X-OT-Signature).

Response

A completed job returns the transcript in the OpenTranscription Unified Schema (OTUS).

{
  "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "status": "completed",
  "transcript": {
    "text": "Welcome to the meeting, everyone.",
    "language": "en",
    "confidence": 0.97,
    "segments": [
      {
        "id": 0,
        "start": 0,
        "end": 3.5,
        "text": "Welcome to the meeting, everyone.",
        "speaker": "A"
      }
    ],
    "words": [
      {
        "word": "Welcome",
        "start": 0,
        "end": 0.42,
        "confidence": 0.99
      }
    ]
  }
}

Webhooks — skip polling

We POST a signed event to your webhook_url when a job completes or fails; verify the X-OT-Signature (HMAC-SHA256, reject if older than 300 s) and dedupe on the event id, then fetch the full transcript via GET /api/v1/transcriptions/{id}.

# We POST a signed event to your webhook_url when a job finishes.
# Headers:
#   X-OT-Signature: t=1736937042,v1=5257a869e7eceb6c6c2c2a1b4d6e9f8c2a1b4d6e9f8c2a1b4d6e9f8c2a1b4d6e
#   X-OT-Event-Id: evt_9f8c2a1b4d6e
#   X-OT-Event-Type: transcription.completed
#
# Body (thin event — fetch the transcript with GET /transcriptions/{data.id}):
{
  "id": "evt_9f8c2a1b4d6e",
  "event": "transcription.completed",
  "created": "2025-01-15T10:30:42.000Z",
  "data": {
    "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "status": "completed",
    "error_code": null
  }
}
#
# Verify: HMAC-SHA256 over "<t>.<raw_body>" with your signing secret,
# constant-time compare against any v1, and reject if |now - t| > 300s.

Rate-limited per tier — see the X-RateLimit-* response headers.

Full API reference

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Supported Languages

EnglishSpanishFrenchGermanItalianPortugueseDutchRussianChineseJapaneseKoreanArabicHindiTurkishPolishUkrainianSwedishDanishFinnishNorwegianIndonesianThaiVietnameseCzechGreek

Supported Formats

mp3wavflacm4aoggwebmaac

Features

Auto-detectDiarizationWord Timestamps

Soniox STT (Async)

Cost vs. accuracy

Performance by category

Performance by accent

Pricing

API & usage

Similar models

About Soniox STT (Async)