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Soniox vs OpenAI
for Bulgarian speech-to-text

Higher accuracy, richer real-time features, and lower cost for Bulgarian transcription.

Developers choose Soniox for real-time, real world Bulgarian fluency

Bulgarian is spoken by 8 million people worldwide — primarily in Bulgaria, with speakers around the world. Soniox delivers production-ready transcription and translation for Bulgarian, handling regional accents, code-switching, and real-world audio conditions. OpenAI lists Bulgarian as supported, but benchmark results show far higher error rates compared to Soniox.

If you need higher real-world accuracy for Bulgarian, live streaming features built for apps, and lower cost at scale, Soniox is the better fit. OpenAI's new Realtime API combines transcription and voice output in one API, designed for full voice agents. But it costs more for lower accuracy than Soniox, and lacks diarization, supports only one-way translation into English, and doesn't provide the structured metadata (timestamps, confidence, manual finalize) that developers rely on.

Higher accuracy in Bulgarian, and 60+ languages

Bulgarian Word Error Rate 5.6% for Soniox vs 17.2% for OpenAI (lower is better).

Live streaming features, out of the box

Real-time token streaming, diarization, and Bulgarian translation in the same stream.

Lower cost, higher value

Pay up to 10x less than OpenAI, which charges more and requires multiple endpoints.

Helping startups and enterprises ship real world voice apps

Samsung
Deliver Health
Avodah
Mobius
Scribe
Agora

See the difference for yourself

Don't just take our word for it. Run the same Bulgarian audio through Soniox and OpenAI in real time and compare live results, side by side.

This demo isn't pre-recorded. It makes real API calls to OpenAI and Soniox in real time, with each service tuned for its best performance. The framework is open source, so you can inspect or run it yourself.

SONIOX VS OPENAI AT A GLANCE

The benchmarks back it up

In a 2025 study across 60 languages and real-world YouTube audio, Soniox reached 5.6% WER in Bulgarian vs 17.2% for OpenAI.

View the full benchmark report

It just gets the words right — any language, any accent, any context. That’s what accuracy is supposed to look like.

Tony Wang,
Cofounder & Chief Revenue Officer at Agora

One call. All features. No compromises.

One API, global by default.

Soniox supports 60+ languages with production-ready accuracy in a single model. One call works for 8 million Bulgarian speakers.

Unlike OpenAI, which splits transcription, translation, and streaming across multiple APIs, and struggles in major languages like Hindi and Mandarin.

Streaming in Bulgarian that feels live.

Token-by-token updates appear in milliseconds and stabilize as words finish. Captions don't lag, and assistants respond in sync.

OpenAI's Realtime API supports live transcription, but without diarization, multi-language translation, or transcript metadata. Soniox includes all of these in one stream.

Designed for real-world Bulgarian speech.

Soniox doesn't stop at transcription. It translates speech in real time, handling accents, slang, overlap, and language shifts with aplomb.

OpenAI only supports one-way translation into English, with no in-stream two-way translation or speaker handling.

Ship faster, with fewer moving parts.

Instead of patching together multiple vendors or APIs, Soniox gives you transcription, translation, and diarization in one call.

With OpenAI, you'll be managing separate endpoints and extra tooling.

Pay 2-10x less than OpenAI

With Soniox, all features are included in one price: transcription, streaming, diarization, translation, and 60+ languages. OpenAI charges more and splits features across different endpoints.

Effective hourly cost

(typical speech)

Soniox

~$0.10/hour (async)
~$0.12/hour (streaming)

OpenAI

~$0.38–$1.15/hour


Soniox and OpenAI Whisper are shown as effective $/hour. OpenAI Realtime API is billed per token. Estimates assume typical conversational speech.

100 hours
1,000 hours
10,000 hours
Soniox (async)
~$10
~$100
~$1,000
Soniox (streaming)
~$12
~$120
~$1,200
OpenAI mini-transcribe
$18
$180
$1,800
OpenAI 4o-transcribe
$36
$360
$3,600
OpenAI Realtime (est $/hr*)
$38-$115
$380-$1,150
$3,800-$11,500

Takeaway

Soniox costs 2–10x less than OpenAI. At scale, enterprises save $200K–$1M+ over 3 years, while getting higher accuracy and richer features.


  • What about OpenAI's new Realtime API?
    OpenAI now charges per token: $32 per million input tokens, $64 per million output tokens
    Works out to ~$0.38/hour for transcription or ~$1.15/hour with audio output.

    Soniox remains ~$0.10–$0.12/hour, with all features included.

Fluent at any speed

Watch Soniox keep up with fast speech in any language

Chinese to English in real time with SONIOX

Chinese to English in real time with SONIOX

Very fast speaking Spanish translated in real time in English with SONIOX!

Very fast speaking Spanish translated in real time in English with SONIOX!

Real time translation from Japanese to English

Real time translation from Japanese to English

Real-Time Translation Demo | From German to English with SONIOX

Real-Time Translation Demo | From German to English with SONIOX

French speech to Text | Leslie Talks About Monster eating a Cake

French speech to Text | Leslie Talks About Monster eating a Cake

Russian to English with SONIOX

Russian to English with SONIOX

Speaking Super Fast in Italian – Soniox still translated every word into English

Speaking Super Fast in Italian – Soniox still translated every word into English

Korean to English in real time with SONIOX

Korean to English in real time with SONIOX

Real-Time from Slovenian to English with SONIOX

Real-Time from Slovenian to English with SONIOX

Valeria Juri Reads Ukrainian Poem “Мовчати” | Live English Translation by Soniox

Valeria Juri Reads Ukrainian Poem “Мовчати” | Live English Translation by Soniox

Frequently asked questions about Soniox vs OpenAI


1.How accurate is Soniox vs OpenAI for Bulgarian?arrow_downward
In benchmarks, Soniox achieved 5.6% WER on real-world Bulgarian audio, compared to 17.2% for OpenAI. This makes Soniox significantly more production-ready for Bulgarian.

2.Can Soniox handle regional Bulgarian accents?arrow_downward
Yes, Soniox is trained to handle messy, real-world audio with varied Bulgarian accents, multiple dialects, and overlapping speech.

3.Is Soniox cheaper than OpenAI?arrow_downward

Yes. Soniox is billed per token, which works out to about $0.10/hour async or $0.12/hour streaming for typical speech (Soniox pricing).
OpenAI's costs are higher:

  • $0.18/hour for gpt-4o-mini-transcribe
  • $0.36/hour for gpt-4o-transcribe (OpenAI pricing).
  • ~$0.38–$1.15/hour for the new Realtime API, depending on whether you generate audio output (OpenAI Realtime)

That means Soniox is typically 2–10x less expensive, while also including features like real-time diarization, translation, and structured transcript metadata by default.


4.Does Soniox support more languages than OpenAI Whisper?arrow_downward

Soniox supports 60+ languages with production-ready accuracy and can translate between any pair of supported languages, including Bulgarian. OpenAI's Whisper was trained on ~99 languages, but production quality is strong only in a few (like English and Spanish). Many others, including widely spoken languages such as Hindi and Mandarin, are effectively unusable for real-world apps.

With Soniox, one API automatically works for 8 billion people worldwide.


5.Does OpenAI include diarization or translation in real time?arrow_downward
No. The Realtime API handles low-latency transcription and voice responses, but does not support diarization, multi-language translation, or transcript metadata. Soniox includes all of these in the same API call.

6.What makes Soniox streaming different from OpenAI?arrow_downward
Soniox streams token-by-token in milliseconds with non-final → final markers, so apps feel instant and stable. OpenAI's Whisper is batch/file-based, and the Realtime API doesn't include diarization or built-in translation.

7.Do I need multiple APIs with OpenAI?arrow_downward
Yes. OpenAI splits transcription (Whisper Audio API), translation, and live streaming (Realtime API) across different endpoints. Soniox provides transcription, translation, diarization, timestamps, and more in one API call.

8.Are Soniox benchmarks public?arrow_downward
Yes. Soniox published a 2025 benchmark study across 60 languages using real-world YouTube audio. In Bulgarian, Soniox achieved 5.6% WER vs 17.2% for OpenAI. The best way to compare tools is to test Soniox vs OpenAI yourself using the live comparison tool.

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