> ## Documentation Index
> Fetch the complete documentation index at: https://doc.rapida.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Text-to-Speech
> Configure TTS providers, voices, languages, pronunciation, ambient audio, and speech delivery for Rapida voice assistants.
Text-to-Speech (TTS) converts the assistant's text response into spoken audio. It controls how the assistant sounds, how quickly users hear the first audio, and how clearly domain-specific terms are pronounced.
```mermaid theme={null}
flowchart LR
A["LLM + tools"] --> B["Assistant text"]
B --> C["Text-to-Speech"]
C --> D["User hears response"]
```
TTS is configured in the **Voice Output** step of a Phone Call, Web Widget, or Web App / SDK deployment.
## Setup flow
Add the TTS provider credential in **Credentials** before configuring the deployment.
Go to **Configure Assistant** -> **Deployments**, create or edit a voice-capable deployment, then open **Voice Output**.
Select the provider that will synthesize assistant responses.
Select the provider-specific model. Some providers optimize for lowest latency, while others optimize for voice quality.
Select the voice ID. For providers that support custom voices, use the custom voice ID when the field allows custom values.
Match the TTS language to the assistant's expected response language and selected voice.
## Supported providers
| Provider | Typical use |
| ------------------------ | ------------------------------------------------------------------ |
| ElevenLabs | Natural voices, custom voices, and brand voice workflows. |
| Deepgram | Low-latency streaming voice output. |
| Azure Cognitive Services | Enterprise Microsoft environments and broad voice catalog support. |
| Google Speech Service | Google Cloud text-to-speech workflows. |
| OpenAI | OpenAI TTS models and voices. |
| AWS Polly | AWS-native neural and standard voices. |
| Cartesia | Low-latency voice AI and expressive voice controls. |
| Rime | Real-time voice synthesis with provider voices. |
| Sarvam AI | Indian language voice output. |
| Resemble AI | Custom and cloned voice workflows. |
| Neuphonic | Low-latency conversational TTS. |
| MiniMax | Voice models from MiniMax. |
| Groq | Low-latency TTS through Groq-supported models. |
| Speechmatics | Speechmatics voice output. |
| NVIDIA | NVIDIA-hosted voice models. |
| Custom TTS | Your own WebSocket-compatible TTS backend. |
## Configuration fields
The exact fields vary by provider, but TTS configuration usually includes:
| Field | What it controls |
| ---------------- | ---------------------------------------------- |
| Credential | Which stored provider credential Rapida uses. |
| Model | The speech synthesis model. |
| Voice | The voice ID or custom voice identifier. |
| Language | The output language or locale. |
| Speed or emotion | Provider-specific controls for speaking style. |
## Advanced speech settings
Open **Show advanced settings** in Voice Output to tune delivery.
| Setting | What it controls | Default |
| -------------------------- | ---------------------------------------------------------------------------------------------------------------- | -------- |
| Ambient | Optional background ambience mixed into output audio. | `none` |
| Ambient Volume | Volume of the selected ambience. | `18` |
| Pronunciation Dictionaries | Built-in pronunciation rules for currencies, dates, times, numbers, addresses, URLs, abbreviations, and symbols. | none |
| Conjunction Boundaries | Words where Rapida can add natural pause boundaries. | none |
| Pause Duration | Pause length at configured conjunction boundaries. | `240 ms` |
### Pronunciation dictionaries
Use pronunciation dictionaries when the assistant must say structured or domain-specific text clearly.
| Dictionary type | Helps with |
| ---------------------------------------------------------------- | ---------------------------------------- |
| `currency` | Prices, amounts, and currency symbols. |
| `date` and `time` | Dates, appointment times, and schedules. |
| `numeral` | Account numbers, quantities, and IDs. |
| `address` | Street addresses and postal details. |
| `url` | Websites and links. |
| `tech-abbreviation`, `role-abbreviation`, `general-abbreviation` | Acronyms and abbreviations. |
| `symbol` | Symbols that should be spoken naturally. |
Add pronunciation dictionaries before user testing. Mispronounced product names, acronyms, prices, dates, and addresses are easy for users to notice.
### Conjunction boundaries
Conjunction boundaries let Rapida add natural pauses around selected words such as `and`, `but`, `or`, `because`, and `while`. This can make long responses easier to listen to.
Use them when:
* The assistant often speaks multi-clause sentences.
* Users need time to understand instructions.
* TTS output feels rushed even when the voice is good.
Avoid overusing them when:
* The assistant already speaks in very short sentences.
* The added pauses make responses feel slow.
## Choosing a provider
| Need | Recommended direction |
| ----------------------- | ----------------------------------------------------------------------------------- |
| Lowest response latency | Use a streaming TTS provider and keep assistant responses short. |
| Natural voice quality | Use a neural or conversational voice model. |
| Brand voice | Use a provider that supports cloned or custom voice IDs. |
| Multilingual speech | Choose a voice that supports the required language, not only a model that lists it. |
| Phone calls | Test the voice over phone audio, not only in browser previews. |
| Private provider | Use [Custom TTS](/integrations/tts/custom). |
## Prompt guidance for better TTS
TTS quality depends on the text the LLM produces. Tune the assistant prompt for spoken responses:
* Keep responses under one or two short sentences.
* Avoid markdown, bullet lists, long tables, and symbols.
* Ask one question at a time.
* Confirm critical values slowly, especially emails, phone numbers, dates, and addresses.
* Write instructions in natural spoken language.
## Troubleshooting
| Symptom | Likely cause | What to adjust |
| --------------------------------- | -------------------------------------- | --------------------------------------------------------------------------------------- |
| First audio starts slowly | TTS model latency or long LLM response | Use lower-latency TTS and shorten assistant responses. |
| Voice mispronounces product names | Missing pronunciation handling | Enable pronunciation dictionaries or use a provider custom voice/pronunciation feature. |
| Voice sounds rushed | Long clauses or no pauses | Add conjunction boundaries and lower prompt response length. |
| Voice sounds unnatural on phone | Voice tested only on browser audio | Test through the target phone deployment and try a clearer voice. |
| Wrong language or accent | Voice and language mismatch | Select a language-matched voice and provider model. |
## Related
See where TTS fits into spoken output configuration.
Configure user speech transcription.
Connect a custom WebSocket speech synthesis provider with DSL rules.
Configure required voice output for phone calls.
Configure optional voice output for custom apps.