Echo cancellation removes echo caused by your microphone picking up your speaker's output. This normally helps to improve the overall quality of the call.
However, if you work in a noisy environment and you do not have a headset, you may experience poor audio quality or no audio at all for the first few seconds of the call. In cases like that, you may want to disable echo cancellation. You can do in the Audio/Video settings of your Circuit client.
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