Realtime Voice API — AI Glossary

A realtime voice API is a speech-to-speech architecture that accepts streaming audio input and returns streaming audio output directly, without the classical STT-then-LLM-then-TTS pipeline. By skipping the intermediate text representation, these systems target sub-second end-to-end latency suitable for natural conversational turn-taking, including barge-in (the user interrupting mid-response). OpenAI's Realtime API and Cartesia's Sonic are leading examples.