What is barge-in?

Without barge-in, a caller who interrupts is simply talked over, and the agent keeps playing audio into a person who has already moved on. It is the single most common reason an otherwise capable agent is described as 'robotic'.

Implementing it is harder than it sounds because the agent's own voice arrives back through the phone line. The system has to distinguish the caller's speech from an echo of its own output, which requires acoustic echo cancellation with a clean reference signal.

The naive approach (cut off whenever the microphone exceeds a volume threshold) fails badly on speakerphone and in noisy rooms, where the agent's own voice and background noise both trip the threshold constantly.