> ## Documentation Index > Fetch the complete documentation index at: https://developers.telnyx.com/llms.txt > Use this file to discover all available pages before exploring further. # AssemblyAI > AssemblyAI TTS provider — multilingual voices for English, Spanish, German, French, Italian, and Portuguese, with telephony-native audio formats. **Voice format:** `AssemblyAI.assemblyai-tts-1.` AssemblyAI is a third-party TTS provider with streamed synthesis. Every AssemblyAI voice can speak any of the six supported languages: choose the voice for its sound, and set `language` to the language of the text. AssemblyAI does not detect the language for you. ## Voices AssemblyAI offers 11 voices under `assemblyai-tts-1`. The default voice is `aai-jane`. | Voice | Voice ID | | - | - | | Alba | `AssemblyAI.assemblyai-tts-1.aai-alba` | | Anna | `AssemblyAI.assemblyai-tts-1.aai-anna` | | Charles | `AssemblyAI.assemblyai-tts-1.aai-charles` | | Eve | `AssemblyAI.assemblyai-tts-1.aai-eve` | | George | `AssemblyAI.assemblyai-tts-1.aai-george` | | Jane | `AssemblyAI.assemblyai-tts-1.aai-jane` | | Jean | `AssemblyAI.assemblyai-tts-1.aai-jean` | | Mary | `AssemblyAI.assemblyai-tts-1.aai-mary` | | Michael | `AssemblyAI.assemblyai-tts-1.aai-michael` | | Paul | `AssemblyAI.assemblyai-tts-1.aai-paul` | | Vera | `AssemblyAI.assemblyai-tts-1.aai-vera` | You can also list them with the [Voices API](https://developers.telnyx.com/api-reference/text-to-speech-commands/list-available-voices.md) or the [available voices](https://developers.telnyx.com/docs/voice/tts/available-voices.md) page: ``` GET https://api.telnyx.com/v2/text-to-speech/voices?provider=assemblyai ``` ## Models | Model | Description | | - | - | | `assemblyai-tts-1` | Streaming model. **Default** and the only model accepted. | ## Language Set `language` to the two-letter ISO 639-1 code of the text. The default is `en`. A regional code such as `es-MX` is accepted and treated as `es`. Any other language is rejected with an error. | Code | Language | | - | - | | `en` | English | | `es` | Spanish | | `de` | German | | `fr` | French | | `it` | Italian | | `pt` | Portuguese | The text is read as written. Where the reading matters, write numbers, dates, and amounts out in words: a date such as `3/4` or an amount with cents can be read in a way you did not intend. SSML is not supported, and there are no speed, pitch, or emotion controls. Send plain text. ## Voice Settings | Field | Type | Default | Description | | - | - | - | - | | `language` | string | `en` | Two-letter ISO 639-1 code of the text. | | `audio_format` | string | `mp3` | `mp3`, `wav`, `pcm_s16le`, `pcm_mulaw`, or `pcm_alaw`. | | `sample_rate` | integer | `24000` (`8000` for `pcm_mulaw` and `pcm_alaw`) | `8000`, `16000`, `22050`, `24000`, `44100`, or `48000`. | ## Limits A request accepts up to 5,000 characters. Split longer text into several requests. AssemblyAI is a third-party provider that synthesizes speech in the United States. Requests that require in-transit data locality are refused. See [Data Residency](https://developers.telnyx.com/docs/inference/data-residency.md). *** ## WebSocket AssemblyAI is available on the [TTS WebSocket API](https://developers.telnyx.com/docs/voice/tts/websocket-streaming.md). Select the voice with the `voice` query parameter and pick the output with `audio_format` and `sample_rate`. Send `language` in `voice_settings` on the init frame. ``` wss://api.telnyx.com/v2/text-to-speech/speech?voice=AssemblyAI.assemblyai-tts-1.aai-jane&audio_format=mulaw ``` ```json theme={null} { "text": " ", "voice_settings": { "language": "es" } } ``` See the [AssemblyAI WebSocket provider page](https://developers.telnyx.com/docs/voice/tts/websocket-streaming/providers/assemblyai) for the accepted formats and sample rates. ## REST API ### Fields | Field | Type | Default | Description | | - | - | - | - | | `language` | string | `en` | Two-letter ISO 639-1 code of the text. | | `audio_format` | string | `mp3` | `mp3`, `wav`, `pcm_s16le`, `pcm_mulaw`, or `pcm_alaw`. | | `sample_rate` | integer | `24000` (`8000` for `pcm_mulaw` and `pcm_alaw`) | `8000`, `16000`, `22050`, `24000`, `44100`, or `48000`. | | `output_type` | string | `binary_output` | `binary_output`, `base64_output`, or `audio_id`. | ```json theme={null} { "text": "Buenos días, ¿en qué puedo ayudarle?", "voice": "AssemblyAI.assemblyai-tts-1.aai-eve", "voice_settings": { "language": "es", "audio_format": "mp3" } } ``` ### Response Default (`binary_output`): chunked audio bytes. With `output_type: "base64_output"`: JSON with base64-encoded audio. With `output_type: "audio_id"`: JSON with an `audio_url` for deferred retrieval. ## Audio Formats & Sample Rates | Format | Default Sample Rate (Hz) | | - | - | | `mp3`, `wav`, `pcm_s16le` | 24000 | | `pcm_mulaw`, `pcm_alaw` | 8000 | `pcm_mulaw` and `pcm_alaw` are raw G.711 with no header, so they can go straight into a call's media stream. ## In-Call Playback AssemblyAI voices work with the Call Control `speak`, `gather_using_speak`, and conference `speak` commands, and with TeXML ``. * Send plain text: `payload_type` must be `text`. * Set `language` to a code for the language of the text, for example `es-ES`. Call Control takes regional codes; AssemblyAI uses the language part (`es`). ```json theme={null} { "payload": "Buenos días, ¿en qué puedo ayudarle?", "voice": "AssemblyAI.assemblyai-tts-1.aai-eve", "language": "es-ES" } ``` ```xml theme={null} Buenos días, ¿en qué puedo ayudarle? ``` See [In-Call Playback](https://developers.telnyx.com/docs/voice/tts/in-call-playback.md) for details. ## AI Assistants Choose an AssemblyAI voice such as `AssemblyAI.assemblyai-tts-1.aai-jane` in the assistant's voice settings, and set `language` to one of `en`, `es`, `de`, `fr`, `it`, or `pt`. Saving an assistant with any other language is rejected. Every voice speaks all six languages, so one voice can serve an assistant that changes language during a call. > [card] [AI Assistants](https://developers.telnyx.com/docs/inference/ai-assistants/no-code-voice-assistant.md) > > Build voice AI assistants using AssemblyAI voices. > [card] [TTS REST API](https://developers.telnyx.com/docs/voice/tts/rest-api.md) > > Generate speech directly with REST TTS requests.