Your audio device is causing poor audio quality, try using another audio advice.
If the problem persists, transfer the call to a landline. To transfer a call, in the Lync 2010 conversation window, click the Transfer button, and do one following:
Click one of your other numbers (such as your mobile phone number).
Click Another Person or Number, and then in the dialog box that is displayed, type in the phone number you want to transfer the call to, and then click OK.
For details about how to improve on audio quality, see Audio Quality FAQ.