Please right click your sound icon in the bottom right of your screen and select "open sound settings."
 There should then be an option on the right hand side called "sound control panel."
Once that is open, please ensure the correct devices are set by clicking the device and clicking the "set default" button in the bottom right. The "recording" tab is for your microphone, and the "playback" tab is for the sound coming to you.
Please let us know if you are still having issues after checking these settings.