If you hear an echo during an audio call, it might be caused by the audio device that another caller is using. Ask others on the call to help check the following:
Turn down their speaker volume to reduce the echo.
If they are using their webcam’s microphone or computer speakers, ask them to use a different audio device.
Make sure the device that they are using is optimized for Microsoft Lync 2010 communications software. For a list of optimized devices, see Phones and Devices for Microsoft Lync 2010.