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Speech-to-text API for AI voice agents

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Why Soniox is the best speech-to-text API for voice agents

“Best” for voice agents isn’t just about top benchmark scores on clean audio, it’s about predictable, reliable behavior in real production systems.

A speech-to-text system for voice agents should:

  • Deliver highly accurate transcription that keeps up with live conversation.
  • Run with ultra-low latency, enabling real-time LLM processing and fast responses.
  • Reliably detect end-of-turn speech so agents respond at the right moment.
  • Perform in real-world conditions with noise, accents, interruptions, and multilingual speech.
  • Scale economically, with pricing that works for high-volume deployments.

Soniox is built around these requirements from the ground up, delivering fast, reliable speech recognition for voice agents across 60+ languages. One unified model supports true multilingual and language-switching speech, without changing configurations, switching models, or restarting streams.

And with real-time transcription starting at ~$0.12 per hour, Soniox makes it practical and cost-effective to deploy voice agents at massive scale in any language, anywhere.

“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

Lowest-latency speech-to-text in practice

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Live transcription & translation

Soniox is built for continuous conversational streams, returning text as speech arrives so agents and downstream LLMs can act before the speaker is done.

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Turn-taking endpoint detection

Built-in endpoint detection emits reliable end-of-turn events, so agents respond at the right moment without fragile silence timers.

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Custom context

Inject product names, jargon, and entities at request time to improve accuracy without maintaining fine-tuned models.

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One model for 60+ languages

A single unified model handles 60+ languages and in-stream language switching, keeping latency stable and global deployments simple.

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Data residency for regulated deployments

Keep speech and transcripts in the required geography for healthcare, finance, legal, and other regulated voice-agent deployments.

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Why it works

Voice agents need speech recognition that is fast, predictable, multilingual, and production-ready. Soniox combines low-latency streaming, turn detection, context control, multilingual accuracy, and regional deployment in one real-time API.

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Use Soniox in popular frameworks

Soniox integrates seamlessly with leading real-time communication platforms, AI frameworks, automation tools, and developer SDKs.

An open source framework and developer platform for building, testing, deploying, scaling, and observing agents in production.

Open source framework for voice and multimodal conversational AI.

Twilio is a cloud-based customer engagement platform (CPaaS) that provides APIs, allowing developers to integrate voice, messaging (SMS, WhatsApp), email, and authentication capabilities into applications.

Open-source development framework designed to build applications powered by large language models (LLMs).

The open-source AI toolkit designed to help developers build AI-powered applications and agents with React, Next.js, Vue, Svelte, Node.js, and more.

Open-source AI SDK with a unified interface across multiple providers. No vendor lock-in, no proprietary formats.

n8n is a powerful, low-code/pro-code workflow automation tool that connects various applications, APIs, and databases to automate tasks.

For voice agents that understand

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Smart voice assistants

Deliver fast, natural voice interactions inside your product to help answer questions, find information, and complete tasks.

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Support agents

Understand customers instantly across 60+ languages — without switching models — to resolve issues faster.

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In-app voice agents

Embed natural voice automation directly into your app, from onboarding and scheduling to self-service, with fast, reliable, structured responses.

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Call routing agents

Detect intent in real time and route callers instantly, even before they finish speaking. No phone menus required.

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Privacy and compliance, built right in

Never stored, never saved.

Audio stays in memory, everything is processed in real-time.

Built for privacy-critical use cases.

Adhering to leading global security, privacy, and compliance standards.

Trusted where privacy matters most.

Used in industries where speech is sensitive, from healthcare to enterprise.

Soniox is Soc 2 Type 2 compliant
Soniox is ISO 27001:2022 compliant
Soniox is HIPAA compliant
Soniox is GDPR compliant
SOC 2 Type 2 · ISO/IEC 27001:2022 · HIPAA · GDPR

Power up your multilingual AI voice agent

Get production-ready speech-to-text transcription and translation in 60+ languages.

AfrikaansAlbanianArabicAzerbaijaniBasqueBelarusianBengaliBosnianBulgarianCatalanChineseCroatianCzechDanishDutchEnglishEstonianFinnishFrenchGalicianGermanGreekGujaratiHebrewHindiHungarianIndonesianItalianJapaneseKannadaKazakhKoreanLatvianLithuanianMacedonianMalayMalayalamMarathiNorwegianPersianPolishPortuguesePunjabiRomanianRussianSerbianSlovakSlovenianSpanishSwahiliSwedishTagalogTamilTeluguThaiTurkishUkrainianUrduVietnameseWelsh

Frequently asked questions about Soniox for voice agents

What is the Soniox Speech-to-Text API?arrow_downward
Soniox provides a real-time speech-to-text API designed for AI voice agents. It converts live audio into text with low latency, supports streaming use cases, and works across more than 60 languages without switching models or restarting the stream.
Is Soniox suitable for building AI voice agents?arrow_downward
Yes. Soniox is designed for real-time voice agent workflows, including streaming transcription, early token delivery, endpoint detection for turn-taking, all configurable through the API.
What makes Soniox a low-latency speech-to-text API?arrow_downward
Soniox uses a real-time streaming architecture that emits transcription results incrementally as audio arrives. This allows voice agents to begin processing speech before an utterance is complete, reducing end-to-end response time.
How does Soniox handle partial and final transcripts?arrow_downward
The streaming API provides non-final transcription tokens followed by finalized tokens. This enables early intent detection, real-time UI updates, and stable downstream processing without parsing entire transcripts.
How does Soniox detect when a user finishes speaking?arrow_downward
Soniox includes built-in endpoint detection that identifies speech boundaries. Voice agents can use these events to decide when to respond without relying on client-side silence timers.
Can I customize transcription behavior for my voice agent?arrow_downward
Yes. The Soniox API is configurable, allowing developers to adjust transcription behavior, including custom context for domain-specific vocabulary, eliminating the need to maintain separate fine-tuned models for different tasks.
Does Soniox support multilingual voice agents?arrow_downward
Yes. Soniox supports consistent multilingual transcription and translation across more than 60 languages using a single real-time model. Language identification happens automatically within the same stream.
Can Soniox handle language switching within a conversation?arrow_downward
Yes. Soniox can recognize and transcribe speech when speakers switch languages mid-sentence or mid-conversation, without requiring stream restarts or language-specific routing.
Is Soniox suitable for regulated industries?arrow_downward
Yes. Soniox supports data residency for regulated environments such as medical and legal use cases, allowing speech and transcript data to remain within required geographic regions while using the same real-time API.
Is audio stored when using the Soniox API?arrow_downward
No. Audio is processed in real time and kept in memory only. Soniox is designed for privacy-critical applications where speech data should not be stored by default.
How do developers get started with Soniox?arrow_downward
Developers can generate an API key on Soniox Console and start streaming audio over websockets to Soniox directly. The API integrates with common voice agent frameworks and real-time media pipelines, making it easy to add speech-to-text to existing systems.