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-powered system that has real-time spoken conversations — over a phone call, a web widget or a SIP trunk — using speech recognition, a language model and speech synthesis.
Voice AI is the umbrella term for AI systems that understand and generate human speech in real time — powering voice assistants, phone agents, voice chatbots and real-time translation.
Conversational AI is the category of AI systems designed to interact with humans in natural language, across chat, voice, email and messaging — using NLU, LLMs and tool-calling to hold multi-turn conversations that actually accomplish work.
IVR is a rigid scripted decision tree (press 1 for sales). Voice AI is a natural-language agent that understands free-form speech, uses LLM reasoning, and calls tools to take real actions.
BYOK means you bring your own API keys for the LLM, STT and TTS providers, and the voice AI platform routes usage through your accounts instead of bundling the provider costs into its own pricing.
BYON means you bring your own phone number — via a Twilio, Vobiz or Exotel account — and connect it to the voice AI platform via SIP, instead of renting a number from the platform itself.