The speaker or audio device you’re using is not working correctly. Make sure the audio device is plugged in correctly and also check the volume settings on the device. If there is physical damage to the device or if the problem continues after restarting your computer, try using a different device. Additionally, make sure that the device you’re using is optimized for Microsoft Lync Online communications software. For a list of optimized devices, see Phones and Devices Qualified for Microsoft Lync.
In the lower-left corner of the Lync main window, click the audio device menu, and then click Check Call Quality to make a test call and hear how you sound using the selected device.
While waiting for resolution on the issue, enable call forwarding or simultaneous ring so that incoming calls get routed to another phone and don’t get missed. For steps about how to set up call forwarding and simultaneous ring, see Call forward and simultaneous ring. If the problem persists, transfer the call to a different phone number. To transfer a call, in the Lync conversation window, click the Transfer button, and do one of the following:
Click one of your other numbers (such as your mobile phone number).
Click Another Person or Number, and in the dialog box that is displayed, type the phone number you want to transfer the call to, and then click OK.