Hi there! 👋 I wasn't able to find specific information about a "sonic turbo" model, but I can definitely help you with using Cartesia's sonic voice models in your Vapi assistant! According to the [changelog documentation](https://docs.vapi.ai/changelog/2024/12/30), you can use

sonic

and

sonic-preview

models in your Vapi assistant. Here's how to set it up: 1. In your Vapi assistant configuration, you'll need to configure the Voice component (one of the three core components of a Vapi assistant alongside Transcriber and Model). 2. You can set up your assistant configuration like this:

javascript
const assistant = {
  model: {
    provider: "openai",
    model: "gpt-3.5-turbo",
    systemPrompt: "Your system prompt here",
  },
  voice: {
    provider: "cartesia",
    voiceId: "sonic", // or "sonic-preview"
  },
  firstMessage: "Hi, how can I assist you today?",
};

3. For additional customization, Cartesia voices support experimental controls. According to the [documentation](https://docs.vapi.ai/changelog/2025/2/25), you can specify voice speed and emotional range with:

javascript
voice: {
  provider: "cartesia",
  voiceId: "sonic",
  experimentalControls: {
    speed: "fast", // or other speed settings
    emotionalRange: ["happy", "excited"] // example emotional ranges
  }
}

You can configure your assistant either through the Vapi dashboard or by using the API with a PATCH request to update your assistant configuration. Is there anything specific about the Cartesia voice models you'd like to know more about? Sources: - [https://docs.vapi.ai/changelog/2024/12/30](https://docs.vapi.ai/changelog/2024/12/30) - [https://docs.vapi.ai/assistants](https://docs.vapi.ai/assistants) - [https://docs.vapi.ai/examples/voice-widget](https://docs.vapi.ai/examples/voice-widget) - [https://docs.vapi.ai/changelog/2025/2/25](https://docs.vapi.ai/changelog/2025/2/25)

@simon84734 Here's a step-by-step guide: Step 1: Configure DTMF Input Detection First, you need to enable keypad input processing in your Vapi assistant. This ensures that when a user presses "0", Vapi can detect it and take action. In your assistant configuration, enable the keypad input plan:

javascript
// Assistant configuration
{
  // Other assistant config...
  keypadInputPlan: {
    enabled: true,
    timeoutSeconds: 0,  // Process each key press immediately
    delimiters: []  // No delimiters needed for single key detection
  }
}

Step 2: Add a transferCall Tool to Your Assistant Add a

transferCall

tool to your assistant that includes the external voicemail number as a destination:

javascript
// Assistant configuration with transferCall tool
{
  // Other assistant config...
  model: {
    // Other model config...
    tools: [
      {
        type: "transferCall",
        destinations: [
          {
            type: "number",
            number: "+1234567890", // Replace with your voicemail number
            message: "Transferring you to voicemail now..."
          }
        ]
      }
    ]
  }
}

Step 3: Add Logic to Handle DTMF "0" Input In your assistant's prompt/system message, include instructions to transfer the call when "0" is pressed:

System: You are a helpful voice assistant. When a user presses 0 on their keypad, immediately transfer the call to voicemail.

If you detect that a user has pressed the 0 key (which will appear in the conversation as "User's Keypad Entry: 0"), use the transferCall tool to transfer them to the voicemail number without asking for confirmation.

Step 4: Testing Your Implementation Once configured, test your setup by calling your Vapi number and pressing "0" during the conversation. The assistant should detect the keypress and automatically transfer the call to your configured voicemail number.

How can I use sonic turbo in my vapi assistant?

You can raise an feature request for it over here: https://roadmap.vapi.ai