Building “Jarvis”: How to Create a Real-Time Voice AI (That Actually Listens)

by

🛑 Stop typing. Start talking. The keyboard is obsolete.

We have all tried Siri or Alexa. You ask a question. You wait. ⏳ You wait. ⏳ It answers robotically. If you try to interrupt? It keeps talking. 😤

That isn’t a conversation; that’s a lecture.

But in late 2025, Multimodal Audio-to-Audio technology changed the game. We can now build AI agents that listen, think, and speak in real-time (sub-300ms latency). You can interrupt them, laugh at their jokes, and hear them sigh when they are thinking.

Today, we are building Jarvis. 🦾

⚡ The Architecture: Why REST APIs Are Dead

To build a truly conversational AI, we have to abandon the old way.

❌ The Old “Slow” Way (3-5 Seconds Latency):

  1. Record Audio 🎤 ->
  2. Transcribe to Text (Whisper) 📝 ->
  3. Send to LLM (GPT-4) 🧠 ->
  4. Text to Speech (ElevenLabs) 🗣️ ->
  5. Play Audio 🔊

✅ The New “Real-Time” Way (300ms Latency):

  1. Open a WebSocket 🔌
  2. Stream Audio In 🌊
  3. Stream Audio Out 🌊

The AI model (like OpenAI’s GPT-4o Realtime) processes the sound itself, capturing your tone, emotion, and hesitation.

🧰 The “Iron Man” Tech Stack

  • 🧠 The Brain: OpenAI Realtime API (Handles listening, thinking, and speaking).
  • ⚛️ The Interface: React + TypeScript (For the visualizer).
  • 📡 The Protocol: WebSockets (For the live data stream).
  • 🔊 The VAD: Voice Activity Detection (To handle interruptions).

🔌 Step 1: The WebSocket Connection

We don’t use POST requests here. We need a persistent, live telephone line to the AI.

JavaScript

// Connect to the Realtime API
const pc = new RTCPeerConnection();
const ws = new WebSocket("wss://api.openai.com/v1/realtime?model=gpt-4o-realtime-preview");

ws.onopen = () => {
    console.log("⚡ Connected to Jarvis.");
};

When this connection opens, the AI is “listening.”

🗣️ Step 2: Handling “Barge-In” (Interruptions)

This is the feature that makes the AI feel human. If the AI is talking and you say, “Wait, actually…”—it needs to stop immediately.

We use VAD (Voice Activity Detection).

  1. Browser mic detects sound. 🎤
  2. App sends input_audio_buffer.commit event. 📨
  3. AI receives event -> Cancels current audio output. 🔇
  4. AI listens to your new command. 👂

It feels like magic. It feels like talking to a friend on the phone.

🎨 Step 3: The Visualizer (Making it Look Cool)

A voice assistant needs a face. In 2025, the trend is Fluid Audio Visualizers (like the floating orb in Apple Intelligence).

We use the Web Audio API to analyze the frequency data of the returned audio and animate a canvas.

  • User Speaking: Orb glows Green 🟢 (Pulsing with your voice).
  • AI Thinking: Orb spins Blue 🔵.
  • AI Speaking: Orb ripples Purple 🟣.

TypeScript

// Simple logic for the visualizer state
<div className={`orb ${isUserSpeaking ? 'pulse-green' : 'ripple-purple'}`}>
  {/* Your CSS magic goes here */}
</div>

🤖 Step 4: Adding Personality

Don’t make a boring assistant. Make a character.

In the session.update configuration, we give Jarvis his instructions:

“You are Jarvis, a witty, sarcastic, and highly intelligent assistant. You speak quickly. You are allowed to use filler words like ‘hmm’ or ‘let me see’ to sound natural. If the user is wrong, correct them gently but firmly.”

Because the model is Audio-to-Audio, it can actually act sarcastic. It can whisper if you whisper. It can shout if you shout. 🤯

🚀 The “Wow” Demo

Imagine recording this for TikTok or YouTube:

  1. You: “Hey Jarvis, help me debug this code.”
  2. Jarvis: “Alright, let’s see the mess you’ve made this ti—”
  3. You (Interrupting): “Hey! Be nice!”
  4. Jarvis (Instantly stops): “My apologies. I’ll be gentle. Show me the code.”

That instant interruption? That’s the viral moment. That is the future of Human-Computer Interaction (HCI).

🔮 Why This Matters

We are moving away from Screens and toward Ambient Computing.

  • Customer Service: Agents that don’t sound like robots.
  • Therapy: AI that can hear the sadness in your voice.
  • Language Learning: Tutors that correct your accent in real-time.

Stop building for the keyboard. Build for the voice.

Suit up. 🦾✨