A fix to no audo problem with nexus 4 and cyanogenmod 11 as described at xda
The application hooks to call status and disables the CheckinService when call is active then activates it after the call is finished. REQUIRES ROOT.
Not tested on anything besides Nexus 4 with cm-11-20141115-SNAPSHOT-M12-mako.
Download the latest release and install on your Nexus 4.
Run the app and click the enable button. Then try to call. If this doesn't work, try to reboot the device.