Web Browser Audio (WebRTC) Microphone Behavior

Firefox 156 and Chrome 153 (and probably all other 2026 browsers, too) apply echo cancellation to microphone inputs by default. Individual websites can request that the echo cancellation be disabled, but this is often invisible to the user. The algorithms used by Firefox and Chrome are also very aggressive. Repetitive vocalizations (like "ahhhhhh..." or "du du du du...") stutter or go completely silent. Speaking in a monotone voice can also produce audio reminiscent of packet loss or of a faulty setup.

The algorithm kicks into high gear if the browser outputs (to speakers or headphones) its input (from a microphone). This behavior causes problems in many web-based microphone testers (e.g., those in the web clients of Discord and Microsoft Teams, and other standalone pages).

Observations

On both Firefox 156 and Chrome 153, turning off echoCancellation will default autoGainControl and noiseSuppression to disabled. The web application (or the user, if the web application exposes those settings) may explicitly request that those be re-enabled. This is an intended behavior.

Both browsers also seem to apply negative gain to microphones when autoGainControl is off. I've not found any documentation for this, but it's too consistent to be an accident. Thus, for many web VoIP applications, disabling echoCancellation and enabling autoGainControl will yield the clearest audio.

Of course, programmers can do whatever they want with audio data, so they may be applying their own filters on top of the browser's. There's no magic bullet.

Microphone Test Sandbox

The following tool may help experiment with these behaviors. It might also help debug other microphone issues. Tick the "Run?" checkbox below to start. By increasing the delay, you can make it harder for the echo cancellation to distort speech. Experiment with toggling echoCancellation and loopback, and observe how the FFT waveform varies.

None of those behaviors appear to be affected by other sources of audio, like on-page media playback.

This works completely offline; the audio is not transmitted anywhere.