Voice AI Agent
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.
A voice AI agent is an AI-powered system that can hold real-time spoken conversations with a human. It converts the human's voice to text using speech-to-text (STT), feeds the text to a large language model (LLM) which decides how to respond and which tools to call, then converts the LLM's response back to speech using text-to-speech (TTS) — all within a few hundred milliseconds per turn. Voice AI agents run on web widgets, phone calls, and SIP trunks, and can call external APIs to take real actions like booking appointments or updating a CRM.
The three-part stack
Every voice AI agent is built on the same three layers:
- Speech-to-Text (STT): The user's voice is transcribed into text in real time. Popular providers include Deepgram, Sarvam Saaras, AssemblyAI and Whisper.
- Language model (LLM): The text is sent to an LLM like GPT-4o, Claude, Gemini, Groq or Sarvam LLM. The LLM decides the response — and may call tools (functions) to look up data, book appointments, or trigger downstream actions.
- Text-to-Speech (TTS): The LLM's response is converted back to human speech using a TTS provider like ElevenLabs, Cartesia, Sarvam Bulbul or OpenAI TTS.
What makes it different from an IVR
An IVR follows a scripted decision tree — press 1 for sales, press 2 for support. A voice AI agent uses natural language understanding — the caller can say anything, and the agent understands intent, asks follow-up questions, calls external tools to look things up, and responds conversationally.
Typical latency budget
For conversational quality, a voice AI agent needs to respond within 500–800ms from the end of the user's speech. That budget is split across STT (~100–200ms), LLM (~150–400ms), TTS (~150–300ms), plus network round-trip.
Common use cases in India
Debt collections, BFSI customer service, EMI reminders, appointment booking, lead qualification for real estate, cart recovery for D2C brands, student counseling for EdTech, and citizen helplines for government services.
More definitions
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.
SIP trunking is the protocol that lets a voice AI platform send and receive phone calls over the internet, connecting to the public phone network via a carrier like Twilio or Vobiz.