What is Echo cancellation?

Echo cancellation is the audio processing that removes a speaker's own voice when it leaks back into the call, for example when sound from a phone's loudspeaker is picked up again by its microphone and sent to the other end. Echo happens because audio played into a handset can be captured by the same device a fraction of a second later. The far end then hears their own words repeated with a delay, which is distracting for a person and even worse for a voice agent, because the agent can mistake its own reply, or the caller's echoed speech, for something new that the caller said. Echo cancellers compare what was sent with what came back and subtract the matching part from the incoming signal.

A voice agent that hears an echo of itself may stop mid-sentence, answer its own words or fail to detect when the caller has really finished speaking. This matters most on speakerphone calls, which are common in Indian homes, offices and vehicles, and on long call paths through several carriers where delay makes echo more noticeable. Echo handling works together with barge-in and turn-taking: the agent must tell the difference between the caller interrupting and its own voice returning down the line.