DocsAgentsAdding Voice

Adding Voice to Agents

Mastra agents can be enhanced with voice capabilities, allowing them to speak responses and listen to user input. You can configure an agent to use either a single voice provider or combine multiple providers for different operations.

Using a Single Provider

The simplest way to add voice to an agent is to use a single provider for both speaking and listening:

import { createReadStream } from "fs";
import path from "path";
import { Agent } from "@mastra/core/agent";
import { OpenAIVoice } from "@mastra/voice-openai";
import { openai } from "@ai-sdk/openai";
 
// Initialize the voice provider with default settings
const voice = new OpenAIVoice();
 
// Create an agent with voice capabilities
export const agent = new Agent({
  name: "Agent",
  instructions: `You are a helpful assistant with both STT and TTS capabilities.`,
  model: openai("gpt-4o"),
  voice,
});
 
// The agent can now use voice for interaction
await agent.voice.speak("Hello, I'm your AI assistant!");
 
// Read audio file and transcribe
const audioFilePath = path.join(process.cwd(), "/audio.m4a");
const audioStream = createReadStream(audioFilePath);
 
try {
  const transcription = await agent.listen(audioStream, { filetype: "m4a" });
} catch (error) {
  console.error("Error transcribing audio:", error);
}

Using Multiple Providers

For more flexibility, you can use different providers for speaking and listening using the CompositeVoice class:

import { Agent } from "@mastra/core/agent";
import { CompositeVoice } from "@mastra/core/voice";
import { OpenAIVoice } from "@mastra/voice-openai";
import { PlayAIVoice } from "@mastra/voice-playai";
import { openai } from "@ai-sdk/openai";
 
export const agent = new Agent({
  name: "Agent",
  instructions: `You are a helpful assistant with both STT and TTS capabilities.`,
  model: openai("gpt-4o"),
 
  // Create a composite voice using OpenAI for listening and PlayAI for speaking
  voice: new CompositeVoice({
    listenProvider: new OpenAIVoice(),
    speakProvider: new PlayAIVoice(),
  }),
});

Working with Audio Streams

The speak() and listen() methods work with Node.js streams. Here’s how to save and load audio files:

Saving Speech Output

import { createWriteStream } from "fs";
import path from "path";
 
// Generate speech and save to file
const audio = await agent.speak("Hello, World!");
const filePath = path.join(process.cwd(), "agent.mp3");
const writer = createWriteStream(filePath);
 
audio.pipe(writer);
 
await new Promise<void>((resolve, reject) => {
  writer.on("finish", () => resolve());
  writer.on("error", reject);
});

Transcribing Audio Input

import { createReadStream } from "fs";
import path from "path";
 
// Read audio file and transcribe
const audioFilePath = path.join(process.cwd(), "/agent.m4a");
const audioStream = createReadStream(audioFilePath);
 
try {
  console.log("Transcribing audio file...");
  const transcription = await agent.listen(audioStream, { filetype: "m4a" });
  console.log("Transcription:", transcription);
} catch (error) {
  console.error("Error transcribing audio:", error);
}

Real-time Voice Interactions

For more dynamic and interactive voice experiences, you can use real-time voice providers that support speech-to-speech capabilities:

import { Agent } from "@mastra/core/agent";
import { OpenAIRealtimeVoice } from "@mastra/voice-openai-realtime";
import { search, calculate } from "../tools";
 
// Initialize the realtime voice provider
const voice = new OpenAIRealtimeVoice({
  chatModel: {
    apiKey: process.env.OPENAI_API_KEY,
    model: 'gpt-4o-mini-realtime',
  },
  speaker: 'alloy'
});
 
// Create an agent with speech-to-speech voice capabilities
export const agent = new Agent({
  name: 'Agent',
  instructions: `You are a helpful assistant with speech-to-speech capabilities.`,
  model: openai('gpt-4o'),
  tools: { // Tools configured on Agent are passed to voice provider
    search,
    calculate
  },
  voice
});
 
// Establish a WebSocket connection
await agent.voice.connect();
 
// Start a conversation
agent.voice.speak("Hello, I'm your AI assistant!");
 
// Stream audio from a microphone
const microphoneStream = getMicrophoneStream();
agent.voice.send(microphoneStream);
 
// When done with the conversation
agent.voice.close();

Event System

The realtime voice provider emits several events you can listen for:

// Listen for speech audio data sent from voice provider
agent.voice.on('speaking', ({ audio }) => {
  // audio contains ReadableStream or Int16Array audio data
});
 
// Listen for transcribed text sent from both voice provider and user
agent.voice.on('writing', ({ text, role }) => {
  console.log(`${role} said: ${text}`);
});
 
// Listen for errors
agent.voice.on('error', (error) => {
  console.error('Voice error:', error);
});