Glossary · Business

Voice AI

Voice AI is the stack that lets computers understand and speak natural conversation. Definition, components, top platforms, and SMB use cases.

By Kadin Nestler · May 28, 2026 · Updated May 28, 2026
On this page

The voice AI stack in 2026

  • Speech-to-text (STT) — Deepgram, AssemblyAI, OpenAI Whisper. Sub-300ms streaming transcription.
  • Large language model — Claude, GPT-4o, Gemini. The reasoning layer that decides what to say.
  • Text-to-speech (TTS) — ElevenLabs, Cartesia, PlayHT. Human-sounding synthesis under 200ms.
  • Orchestration platform — Vapi, Retell, Synthflow, LiveKit. Glues STT + LLM + TTS into a phone call.
  • Telephony — Twilio, Telnyx. The actual phone number and call routing.

What good voice AI feels like

End-to-end latency under 800ms — the time from a caller finishing a sentence to the AI starting its reply. Below that threshold, most callers do not consciously notice they are talking to AI. The agent handles interruptions (the caller cuts in mid-reply), backchannels (the caller says "mhm" while listening), and barge-in (the caller starts a new question without waiting). The 2025-2026 wave of voice platforms made all of this commodity infrastructure.

Where voice AI fits in an SMB

  • Inbound receptionist — answers every call, qualifies, books, writes to CRM.
  • Missed-call recovery — calls back missed callers within seconds.
  • Outbound qualification — confirms appointments, runs renewal check-ins.
  • Voicebot for waitlists, prescription refills, basic FAQ.
  • After-hours coverage for businesses that cannot staff 24/7.

Cost in 2026

Voice AI infrastructure runs roughly $0.05-$0.15 per minute of conversation, mostly model and TTS costs. Agency build for SMB scope: $1,500-$6,000. Monthly retainer for operation and tuning: $149-$1,500/mo. All-in, a well-built AI receptionist usually lands at $300-$700/mo including platform passthrough — compared to a human receptionist at $3,000-$4,500/mo.

What it means for your business

For service businesses with phone-driven intake (trades, insurance, legal, medical, real estate), voice AI is usually the highest-ROI first deployment. Every captured missed call is recovered revenue.

  • AI Receptionist — An AI receptionist answers calls 24/7, books appointments, and writes to your CRM. Definition, pricing, and how it compares to a human receptionist.
  • Conversational AI — Conversational AI is software that holds natural dialogue with users in text or voice. Definition, evolution, and what separates working systems from demos.
  • AI Agent — An AI agent is an LLM-driven program that uses tools to complete tasks autonomously. Definition, architecture, and real SMB examples.
  • Customer Service AI — Customer service AI is the stack of LLM-powered agents handling support tickets, chat, voice, and email. Definition, top vendors, and ROI math.
  • AI Automation — AI automation uses LLMs and agents to handle work that traditional automation cannot. Definition, examples, and the build-vs-buy math.
← Back to the full glossary