Clear Conversations, No Echo

Echo-ul degradează conversația și poate confuza STT-ul. AEC (Acoustic Echo Cancellation) elimină feedback-ul audio.

Types of Echo

Acoustic Echo

Sound from speaker picked up by microphone in same room.

🔊→🎤

Speaker output → Room acoustics → Microphone input

Common with speakerphones, laptops, smart speakers

Line (Hybrid) Echo

Signal reflection at 2-wire/4-wire conversion points in PSTN.

4-wire↔Hybrid↔2-wire

Impedance mismatch causes signal reflection

Common in PSTN gateways, international calls

How AEC Works

Reference Signal Capture

AEC captures the audio being sent to the speaker (far-end signal).

Estimate Echo Path

Adaptive filter learns how far-end signal appears in microphone input (room acoustics, delays, frequency response).

Generate Anti-Echo

Create inverted estimate of echo component.

Subtract from Microphone

Remove echo while preserving near-end speaker's voice.

AEC Signal Flow

Far-end audio (from caller)
       │
       ▼
   ┌───────┐
   │Speaker│ ──────────────────────────┐
   └───────┘                           │ (acoustic path)
                                       ▼
   ┌───────┐     ┌─────────┐     ┌──────────┐
   │  Mic  │ ──► │  AEC    │ ──► │ Clean    │ ──► To STT/Recording
   └───────┘     │ Filter  │     │ Output   │
       ▲         └────┬────┘     └──────────┘
       │              │
       │         Reference signal (speaker output)
       │
  Near-end speaker (local user)

AEC Parameters

Tail Length

How far back to look for echo

128ms

Suppression Level

Aggressiveness of echo removal

High

Convergence Rate

How fast filter adapts

0.5

ERLE Target

Echo Return Loss Enhancement

>30dB

Echo Metrics

42dB

ERLE

Echo suppression

0.3%

Residual Echo

Remaining after AEC

78ms

Echo Delay

Path delay detected

98%

Convergence

Filter stability

Double-Talk Detection

When both parties speak simultaneously, AEC must not remove the near-end voice:

Far-End Only

Only caller speaking. AEC adapts and subtracts echo.

Normal operation

Near-End Only

Only local user speaking. AEC passes through.

Pass-through mode

Double-Talk

Both speaking. AEC freezes adaptation to protect near-end.

Freeze & protect

Voice AI Considerations

Why Echo Matters for Voice AI

• STT hears AI's own speech → transcription errors
• Barge-in detection fails
• User frustration from hearing themselves
• Call quality scores drop

Best Practices

✓ Apply AEC before STT input
✓ Use reference signal from TTS output
✓ Monitor ERLE in production
✓ Test with various device types

WebRTC AEC

// Enable WebRTC echo cancellation
const constraints = {
  audio: {
    echoCancellation: true,
    echoCancellationType: 'system', // or 'browser'
    autoGainControl: true,
    noiseSuppression: true,
  }
};

const stream = await navigator.mediaDevices
  .getUserMedia(constraints);

// Check if AEC is actually enabled
const track = stream.getAudioTracks()[0];
const settings = track.getSettings();
console.log('Echo cancellation:', settings.echoCancellation);

Crystal Clear Voice

Echo cancellation pentru conversații fără distorsiuni.

Vezi Demo →

Echo Cancellation