Introduction: The Acoustic Proctor
Beside gaze-tracking computer vision, the Duolingo English Test secure browser deploys highly sensitive acoustic analysis algorithms. Their primary task is to detect background voices, whispers, or secondary keyboards that could indicate unauthorized assistance. Unfortunately, these algorithms are often *too* sensitive, flagging harmless ambient noises—such as a distant neighbor speaking, street traffic, or even the hum of a computer fan—as *"External Voice Detected"*, resulting in immediate score cancellation. In this comprehensive guide, we explain the acoustic thresholds used by the DET, show you how to configure your hardware, and lay out the steps to acoustically isolate your room.
1. Acoustic Threshold & Frequency Parameters
The audio proctoring system isolates and evaluates the frequencies recorded by your microphone:
| Frequency / Parameter | Detection Range | Proctor AI Interpretation | Prevention Action |
|---|---|---|---|
| Human Vocal Range | 85 Hz to 255 Hz | Any secondary human voice within this range will trigger an instant flag. | Seal doors and windows with weatherstripping; practice absolute environmental silence. |
| Keystroke Transient Noise | High-frequency sharp spikes | Rapid, mechanical keyboard typing that doesn't match your on-screen typing. | Do not use loud mechanical keyboards. Opt for a silent membrane keyboard. |
| Acoustic Noise Floor | Constant low hums (below -40dB) | High background noise floor degrades your speech, causing transcription failure. | Turn off air conditioners, fans, or heaters in your testing room. |
2. Rules for Hardware Calibration
Your hardware configuration is your primary defense against acoustic invalidations. Follow these calibration rules before opening the secure browser:
- Use a Directional Microphone: Utilize a high-quality external microphone with a cardioid (directional) pickup pattern. This naturally ignores sounds coming from the sides and back, isolating only your voice.
- Calibrate Microphone Gain: Access your system settings and manually adjust your microphone gain. High gain picks up distant noises; keep gain at a moderate level (approx. 70%) to capture only close-range sound.
- Disable Audio Enhancements: Turn off any software noise-suppression or echo-cancellation features in Windows or macOS, as the secure browser client requires raw, unmanipulated audio inputs.
3. The Appeal Framework for Acoustic Flags
If your test is canceled due to an external voice, submit an appeal immediately. State clearly that you were in an isolated room, that the microphone gain was miscalibrated, and request a manual audio review by a human proctor who can easily distinguish distant background noise from actual test assistance.
4. Technical FAQ: Acoustic Proctoring
Q: Can I take the test with headphones or a headset?
A: Absolutely not. The DET rules strictly forbid the use of any headphones, earbuds, or headsets. You must use external speakers and a standalone microphone.
Q: Does speaking too quietly trigger an external voice flag?
A: If you speak in a low whisper, the AI may misclassify your voice as background noise, lowering your transcription accuracy. Speak in a clear, confident, conversational volume.
Q: Can I have a fan running in the room if it is hot?
A: It is highly discouraged. A running fan creates constant ambient white noise, which degrade the audio quality and can trigger system flags.