Echo Cancellation
Definition
The process of removing acoustic echo from an audio signal, preventing speaker output from being re-captured by the microphone.
Echo cancellation removes the sound of system audio output (like the other party's voice in a call) that is picked up by the microphone. Without echo cancellation, the ASR system would attempt to transcribe both the user's speech and the echoed audio, producing garbled results.
Modern echo cancellation uses adaptive filtering to model the acoustic path between the speaker and microphone, then subtracts the estimated echo from the microphone signal. Operating systems provide built-in echo cancellation, but its quality varies. For voice input applications like Ummless, echo cancellation is handled by the OS audio stack before the audio reaches the speech recognition engine.