Turn Detection
Turn detection is how a voice AI agent decides when the caller has finished speaking so it can respond at the right moment.
Turn detection is the real-time decision a voice AI agent makes about when the user has finished their turn and it is time for the agent to respond. Good turn detection combines voice activity detection with semantic end-of-utterance prediction, so the agent waits through natural thinking pauses but still answers quickly once the caller is actually done speaking. It is the single biggest factor in whether a voice agent feels natural.
What turn detection is
In a human conversation, both sides constantly negotiate who is speaking. A voice AI agent has to do the same thing by machine. Turn detection is the component that watches the incoming audio and fires an "end of turn" signal the moment the caller has finished, so the LLM can start generating a reply. Everything the agent does afterwards — thinking, generating, speaking — is gated on this one decision.
Why it is hard
Naive turn detection just waits for silence. That fails constantly: people pause mid-sentence to think, take a breath, or search for a word. If the threshold is too short, the agent cuts them off. If it is too long, the agent feels laggy and dead. Phone audio adds more noise — background chatter, music on hold, dropped packets — all of which confuse a pure silence detector.
How modern turn detection works
Production systems layer two signals. First, voice activity detection (VAD) tells you whether audio currently contains speech. Second, a small machine-learning model predicts whether the words spoken so far look like a complete utterance — a semantic end-of-turn classifier. The agent only commits to responding when VAD reports silence and the semantic model agrees the sentence is finished.
How ThinnestAI handles it
ThinnestAI runs on LiveKit Agents and uses its turn detector under the hood. Thresholds are tunable per agent and per language, which matters in India because end-of-turn prosody in Hindi, Marathi and English is different — speakers trail off, switch languages mid-sentence, and use filler words like "matlab" or "haan". Per-language tuning keeps the agent from interrupting code-switched speech.
More definitions
A voice AI agent is an AI system that holds real-time spoken conversations via phone, web or SIP — combining speech recognition, an LLM and speech synthesis.
Voice AI is the umbrella term for AI that understands and generates human speech in real time — powering voice assistants, phone agents and translation.
Conversational AI is the category of AI that interacts with humans in natural language across chat, voice, email and messaging — using NLU, LLMs and tools.
IVR is a rigid scripted tree (press 1 for sales). Voice AI is a natural-language agent that understands free-form speech, reasons and calls tools.
BYOK lets you bring your own LLM, STT and TTS API keys — the voice AI platform routes usage through your accounts instead of bundling provider costs.
BYON lets you bring your own phone number — via Twilio, Vobiz or Exotel — and connect it to the voice AI platform via SIP instead of renting one.