# Telnyx Voice — Documentation Index > Voice API, speech-to-text, text-to-speech, and voice design. One section of the Telnyx developer docs (https://developers.telnyx.com). > Root index: https://developers.telnyx.com/llms.txt · Full content for this section: https://telnyx.com/llms/voice-full.txt ## Subsections Focused per-subsection files (index + full content): - [Overview](https://telnyx.com/llms/voice/overview.txt) ([full](https://telnyx.com/llms/voice/overview-full.txt)) - [STT](https://telnyx.com/llms/voice/stt.txt) ([full](https://telnyx.com/llms/voice/stt-full.txt)) - [TTS](https://telnyx.com/llms/voice/tts.txt) ([full](https://telnyx.com/llms/voice/tts-full.txt)) - [Voice Design Lab](https://telnyx.com/llms/voice/voice-design-lab.txt) ([full](https://telnyx.com/llms/voice/voice-design-lab-full.txt)) ## Overview - [Overview](https://developers.telnyx.com/docs/voice/overview.md): Overview of Telnyx Voice — standalone components for building voice AI applications, including STT, TTS, programmable voice, WebRTC, and SIP trunking. ## STT - [Overview](https://developers.telnyx.com/docs/voice/stt/overview.md): Real-time and batch audio transcription via WebSocket, REST, or in-call. - [Quickstart](https://developers.telnyx.com/docs/voice/stt/getting-started.md): Stream audio to Telnyx Speech-to-Text and see live transcripts in under 5 minutes with this end-to-end Python and JavaScript quickstart. - [Models](https://developers.telnyx.com/docs/voice/stt/models.md): Compare Telnyx Speech-to-Text engines and models — Deepgram, Whisper, Google, Azure, xAI, AssemblyAI, Speechmatics, Soniox — by accuracy, latency, language coverage, and price. - [Migration](https://developers.telnyx.com/docs/voice/stt/migration.md): Migrate from Deepgram, AssemblyAI, Google, or other speech-to-text providers to Telnyx STT in minutes by changing only two to three lines of code. - [Lifecycle](https://developers.telnyx.com/docs/voice/stt/websocket-streaming.md): How the Telnyx Speech-to-Text WebSocket endpoint works for real-time streaming, including connection, audio frames, transcript messages, and shutdown. - [Overview](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters.md): Reference for query parameters on the Telnyx Speech-to-Text WebSocket endpoint, including engine, model, language, and redaction options. - [Audio Formats](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/audio-formats.md): Supported audio input formats, sample rates, and engine compatibility for the Telnyx Speech-to-Text WebSocket streaming endpoint and binary frames. - [Engines & Models](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/engines-and-models.md): Available speech-to-text engines and models on Telnyx — Deepgram, Telnyx native, Google, Azure, xAI, AssemblyAI, Speechmatics, Soniox — selectable via query parameters. - [End-of-Turn Detection](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/end-of-turn.md): Flux end-of-turn detection parameters for voice agent turn-taking. - [Language](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/language.md): Configure the language for Telnyx Speech-to-Text WebSocket streaming using BCP-47 codes, with per-engine differences in supported languages and behavior. - [Interim Results](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/interim-results.md): Enable interim results to receive partial transcripts as audio streams to the Telnyx Speech-to-Text WebSocket endpoint (Deepgram engine only). - [Endpointing](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/endpointing.md): Configure silence-based endpointing for utterance boundary detection on the Telnyx Speech-to-Text WebSocket endpoint (Deepgram, xAI, Google, Speechmatics, and Soniox). - [Keyword Boosting](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/keyword-boosting.md): Boost recognition of specific terms (keyterm and keywords parameters). - [Redaction](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/parameters/redaction.md): Automatically redact PII such as numbers, names, and SSNs from Telnyx streaming transcription results using Deepgram redaction parameters. - [Messages](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/responses.md): Reference for binary audio frames and JSON message types exchanged over the Telnyx Speech-to-Text WebSocket connection in both directions. - [Errors](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/errors.md): Error codes and troubleshooting tips for the Telnyx Speech-to-Text WebSocket endpoint, including invalid parameters, engine mismatches, and disconnects. - [Examples](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/examples.md): Complete Python and JavaScript code examples for streaming audio to the Telnyx Speech-to-Text WebSocket API and printing live transcription results. - [Production Patterns](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/production-patterns.md): Reconnect, backoff, partial handling, buffering, and monitoring patterns for WebSocket STT. - [Pricing](https://developers.telnyx.com/docs/voice/stt/websocket-streaming/pricing.md): Pricing for Telnyx Speech-to-Text WebSocket streaming. Billed per minute of audio streamed in real time, with model-tier rates and volume discounts. - [Overview](https://developers.telnyx.com/docs/voice/stt/rest-api.md): Transcribe audio files synchronously with the Telnyx Speech-to-Text REST API by uploading a file or providing a public URL and receiving text. - [Overview](https://developers.telnyx.com/docs/voice/stt/rest-api/parameters.md): Reference of all parameters for the Telnyx Speech-to-Text REST API — audio source, language, model, diarization, punctuation, and response options. - [Models](https://developers.telnyx.com/docs/voice/stt/rest-api/parameters/models.md): Available speech-to-text models on the Telnyx STT REST API. Compare general, telephony, and specialty models by language, accuracy, and latency. - [Audio Formats](https://developers.telnyx.com/docs/voice/stt/rest-api/parameters/audio-formats.md): Supported audio formats for the Telnyx Speech-to-Text REST API — WAV, MP3, FLAC, OGG, and more. Includes recommended sample rates and encodings. - [Model Config](https://developers.telnyx.com/docs/voice/stt/rest-api/parameters/model-config.md): Model configuration options for the Telnyx Speech-to-Text REST API — biasing, hotwords, language hints, and per-request tuning of transcription accuracy. - [Response Format](https://developers.telnyx.com/docs/voice/stt/rest-api/parameters/response.md): Response format reference for the Telnyx Speech-to-Text REST API — transcript text, words, timestamps, confidence, and per-channel diarization fields. - [Pricing](https://developers.telnyx.com/docs/voice/stt/rest-api/pricing.md): Pricing for the Telnyx Speech-to-Text REST API. Billed per minute of audio processed, with model-tier rates and volume discounts available on request. - [In-Call Transcription](https://developers.telnyx.com/docs/voice/stt/in-call-transcription.md): Real-time speech-to-text during live Telnyx voice calls via Voice API or TeXML. ## TTS - [Overview](https://developers.telnyx.com/docs/voice/tts/overview.md): Synthesize natural speech from text via WebSocket streaming, REST API, or in-call playback. - [Lifecycle](https://developers.telnyx.com/docs/voice/tts/websocket-streaming.md): How the Telnyx Text-to-Speech WebSocket endpoint works for real-time streaming, including connection, text messages, audio frames, and shutdown signals. - [Configuration](https://developers.telnyx.com/docs/voice/tts/websocket-streaming/configuration.md): Configuration surfaces for Telnyx Text-to-Speech WebSocket streaming, including connection-time query parameters and per-message voice settings. - [Messages](https://developers.telnyx.com/docs/voice/tts/websocket-streaming/messages.md): Reference for WebSocket frame types — client-to-server text messages and server-to-client audio frames — used in the Telnyx Text-to-Speech streaming API. - [Errors](https://developers.telnyx.com/docs/voice/tts/websocket-streaming/errors.md): WebSocket TTS error codes and troubleshooting tips for handshake failures, authentication issues, and runtime streaming errors on the Telnyx platform. - [Examples](https://developers.telnyx.com/docs/voice/tts/websocket-streaming/examples.md): Working Python and JavaScript code samples showing how to stream text-to-speech audio over the Telnyx WebSocket TTS endpoint with basic and advanced setups. - [Overview](https://developers.telnyx.com/docs/voice/tts/rest-api.md): Single-request text-to-speech with HTTP chunked streaming — start playing before synthesis finishes. - [Request](https://developers.telnyx.com/docs/voice/tts/rest-api/request.md): REST TTS request body fields — text, voice, output type, and provider-specific settings. - [Response](https://developers.telnyx.com/docs/voice/tts/rest-api/response.md): REST TTS response formats — streaming audio, base64, and async retrieval. - [Examples](https://developers.telnyx.com/docs/voice/tts/rest-api/examples.md): Code examples for the Telnyx Text-to-Speech REST API showing OpenAI SDK compatibility, synchronous and streaming playback, and async retrieval. - [API Reference](https://developers.telnyx.com/docs/voice/tts/rest-api/api-reference.md): OpenAPI reference for the Telnyx Text-to-Speech REST endpoints, including the generate speech endpoint and request/response schemas for all parameters. - [Overview](https://developers.telnyx.com/docs/voice/tts/providers/telnyx.md): Overview of Telnyx native text-to-speech models, comparing latency, quality, language coverage, and expressive control for the TTS REST API. - [Natural](https://developers.telnyx.com/docs/voice/tts/providers/telnyx/natural.md): Telnyx Natural is a low-latency English text-to-speech model backed by Rime Mist, designed for real-time voice agents and conversational applications. - [NaturalHD](https://developers.telnyx.com/docs/voice/tts/providers/telnyx/naturalhd.md): Telnyx NaturalHD is a high-fidelity multilingual text-to-speech model backed by Rime Arcana, offering studio-quality voices for premium voice applications. - [KokoroTTS](https://developers.telnyx.com/docs/voice/tts/providers/telnyx/kokoro.md): Telnyx KokoroTTS is a lightweight, lowest-latency text-to-speech model ideal for real-time voice agents and interactive applications on the Telnyx TTS API. - [Qwen3TTS](https://developers.telnyx.com/docs/voice/tts/providers/telnyx/qwen3.md): Telnyx Qwen3TTS provides high-quality voice cloning with native support for 11 languages, ideal for multilingual voice agents on the Telnyx TTS API. - [Ultra](https://developers.telnyx.com/docs/voice/tts/providers/telnyx/ultra.md): Telnyx Ultra text-to-speech delivers sub-100ms latency across 44 languages, available exclusively through the TTS REST API for ultra-fast voice synthesis. - [Grok](https://developers.telnyx.com/docs/voice/tts/providers/telnyx/grok.md): xAI Grok voices for expressive, multilingual text-to-speech in Telnyx Voice AI Assistants. - [Rime](https://developers.telnyx.com/docs/voice/tts/providers/rime.md): Configure Rime as a text-to-speech provider on Telnyx with Coda and ArcanaV3 models, voice format strings, speed control, and language coverage. - [Minimax](https://developers.telnyx.com/docs/voice/tts/providers/minimax.md): Configure Minimax as a text-to-speech provider on Telnyx with expressive voices and fine-grained speed, volume, and pitch controls per request. - [Resemble](https://developers.telnyx.com/docs/voice/tts/providers/resemble.md): Configure Resemble AI as a text-to-speech provider on Telnyx using your own Resemble API key, with voice cloning and custom voice support. - [Inworld](https://developers.telnyx.com/docs/voice/tts/providers/inworld.md): Configure Inworld as a text-to-speech provider on Telnyx with Mini low-latency, Max high-quality, and TTS-2 latest-generation models, voice format strings, and language support. - [xAI](https://developers.telnyx.com/docs/voice/tts/providers/xai.md): xAI Grok TTS provider — expressive multilingual voices with speech tags and auto language detection. - [AWS Polly](https://developers.telnyx.com/docs/voice/tts/providers/aws.md): Configure AWS Polly as a text-to-speech provider on Telnyx, with neural, generative, and long-form synthesis engines and voice format strings. - [Azure](https://developers.telnyx.com/docs/voice/tts/providers/azure.md): Configure Microsoft Azure Speech as a text-to-speech provider on Telnyx, with multilingual neural voices, voice format strings, and SSML support. - [ElevenLabs](https://developers.telnyx.com/docs/voice/tts/providers/elevenlabs.md): Configure ElevenLabs as a text-to-speech provider on Telnyx using your own ElevenLabs API key, with voice cloning and premium voice selection. - [Pronunciation Dictionaries](https://developers.telnyx.com/docs/voice/tts/pronunciation-dictionaries.md): Control how specific words are spoken during TTS synthesis with custom pronunciation dictionaries. - [In-Call Playback](https://developers.telnyx.com/docs/voice/tts/in-call-playback.md): Play Telnyx text-to-speech audio during live voice calls using the Programmable Voice API or TeXML, with options for streaming and per-call voice selection. - [Pricing](https://developers.telnyx.com/docs/voice/tts/rest-api/pricing.md): Pricing for the Telnyx Text-to-Speech REST API, including per-character rates by engine, voice tier, and supported provider model. ## Voice Design Lab - [Overview](https://developers.telnyx.com/docs/voice/voice-design-lab.md): Create custom voices from text descriptions or audio recordings, then use them across all Telnyx voice products. - [Overview](https://developers.telnyx.com/docs/voice/voice-design-lab/design-voice/concepts.md): Use AI to generate voices from natural language descriptions — understand the concepts, then create one via the portal or API. - [Quickstart](https://developers.telnyx.com/docs/voice/voice-design-lab/design-voice/quickstart.md): Create a custom synthetic voice step-by-step using the Telnyx Voice Design Lab portal or API, including prompts, reference audio, and provider selection. - [Parameters](https://developers.telnyx.com/docs/voice/voice-design-lab/design-voice/api-details.md): Provider differences and generation parameters for the Voice Design API. - [Prompting Guide](https://developers.telnyx.com/docs/voice/voice-design-lab/design-voice/prompting-guide.md): Write voice descriptions that produce consistent, high-quality results — format templates, dimension guides, and common pitfalls. - [Overview](https://developers.telnyx.com/docs/voice/voice-design-lab/clone-voice/concepts.md): Clone a voice from a short audio recording — capture a speaker's identity from a sample. - [Quickstart](https://developers.telnyx.com/docs/voice/voice-design-lab/clone-voice/quickstart.md): Clone a voice step-by-step — upload a file, record in the browser, or use the API. - [Parameters](https://developers.telnyx.com/docs/voice/voice-design-lab/clone-voice/parameters.md): Models, audio requirements, and async flows for the Voice Clone API. - [Responses](https://developers.telnyx.com/docs/voice/voice-design-lab/clone-voice/responses.md): Reference for the Voice Clone API response, including the voice ID format, status fields, sample audio URLs, and timestamps returned for each clone. - [Errors](https://developers.telnyx.com/docs/voice/voice-design-lab/clone-voice/errors.md): Reference for error codes returned by the Telnyx Voice Clone API, including general errors and provider-specific failures with troubleshooting tips. - [Using Custom Voices](https://developers.telnyx.com/docs/voice/voice-design-lab/using-custom-voices.md): Use your custom voice clones across AI Assistants, Call Control, and the TTS API. ## API Reference (Voice) ### Audio - [Transcribe speech to text](https://developers.telnyx.com/api-reference/audio/transcribe-speech-to-text.md): Transcribe speech to text. This endpoint is consistent with the OpenAI Transcription API and may be used with the OpenAI JS or Python SDK. ### Text To Speech Commands - [Stream text to speech over WebSocket](https://developers.telnyx.com/api-reference/text-to-speech-commands/stream-text-to-speech-over-websocket.md): Open a WebSocket connection to stream text and receive synthesized audio in real time. Authentication is provided via the standard `Authorization: Bearer