If I understand you query correctly, you seem to be 'mixing' the sound card output along with the mike input. Obviously, what you receive is being sent back. Since there is a delay in internet signals from send to receive, the other end receives his sent voice a little later (from your side; and vice versa) causing an echo.
Hope this explains.
Hello,
What is the reason when sterio or mon mix is on then voice chat application gives echo and disturbance in voice.
Thanks in advance
Ravi

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