Ranked #1 in Speech Arena
Conversational AI that talks in real time
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How conversational AI works on a call
Hears the caller
Ink, streaming speech-to-text
Transcribes the caller as they speak, so the text is ready the moment they stop. Built-in turn detection tells a thinking pause from a finished turn.
ExploreDecides what to say
The LLM you choose
Your language model writes the reply. The speech models work the same whichever one you pick.
ExploreTalks back
Sonic, text-to-speech
Starts speaking with sub-90ms time to first audio, then streams the rest of the reply as it's generated. Sonic covers 44 languages and is the #1-ranked TTS model in blind tests.
ExploreFluent and native, worldwide
Reach international markets with Sonic — 44 languages and a wide range of accents, all with native-speaker quality voices.
American English, 3 voices
American English
What is conversational AI?
Conversational AI is software that understands what a person says or types and replies in natural language, across as many turns as the conversation needs. Chat assistants such as ChatGPT are the best-known kind. A voice agent is conversational AI that answers the phone: it can book an appointment or transfer the caller to your team.
Voice is harder than chat because callers don't wait. A chatbot can take three seconds to start a reply; on a call, three seconds of silence sounds like a dropped line. Callers also trail off mid-sentence and talk over the agent, which a text chatbot never has to handle.
How to build conversational AI that takes phone calls
With Cartesia's Managed Agents, you set up a phone agent in three steps, and Cartesia runs the speech models, turn-taking, and phone line.
Choose an LLM and write the instructions
Use the model you already trust. Tell the agent who it is, what it handles, and when to pass the call to a person.
Connect tools, transfers, and a knowledge base
Let the agent look up account details, book appointments, transfer calls to your team, and answer from your own documents.
Get a phone number and take calls
Use a number from Cartesia or bring your own Twilio account or SIP trunk. Cartesia saves each call's audio and transcript for review.
Good for
- Customer support and help desks
- Receptionists and scheduling
- Call-center automation
- Characters, avatars, and toys
Explore more voice tools
FAQs
What is a conversational AI platform?
A conversational AI platform is software for building and running conversational agents. It passes what the user says to a language model, returns the reply, and provides the phone lines, tool connections, and call records around each conversation. Cartesia's platform is built for voice: streaming speech-to-text and text-to-speech models, plus Managed Agents to run phone agents end to end.
Is ChatGPT a conversational AI?
Yes. ChatGPT is conversational AI that works mainly in text. A voice agent does the same job on a live call, which adds real-time work: transcribing speech as it arrives and replying without a gap.
What is voice conversational AI?
Voice conversational AI is conversational AI you speak with rather than type to. It transcribes what you say, gets a reply from a language model, and speaks that reply fast enough for a natural back-and-forth. Phone agents, voice assistants, and talking characters all use it.
How fast does a voice agent need to respond?
Fast enough that the caller never wonders whether anyone is still on the line. In studies of human conversation, a gap of more than about 700 milliseconds before a reply tends to signal a "no". Cartesia's text-to-speech starts streaming with sub-90ms time to first audio, which leaves most of that time for speech-to-text and your LLM.
Can I try Cartesia's voice agents for free?
Yes. The Free plan includes prepaid voice agent usage every month, and you can sign up without a credit card.
Can I use Cartesia's speech models in my own voice agent stack?
Yes. Ink (speech-to-text) and Sonic (text-to-speech) are available through the API and SDKs, so you can run your own pipeline without Managed Agents.
Is Cartesia secure enough for customer calls?
Yes. Cartesia is SOC 2 Type II certified and supports HIPAA and GDPR. Enterprise plans add DPAs and BAAs, SSO, and on-premises or VPC deployment.
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Talk to an expert.
Connect with a member of our team and learn how Cartesia can help you build world-class voice experiences.
Start building.
Access our models via API and bring a voice agent into production in minutes.