The Realtek High Definition Audio Driver should be compatible with Ciso (Softphone) IP communicator. If you have no sound while using the Cisco application, I recommend you update the audio drivers. Just access the official web page, check the box next to I accept to the above, click Next and download the drivers. After that, press Windows + R key combination, type devmgmt.msc and click OK. Expand the Sound, video and game controllers list, right-click on the audio driver and select Update Driver Software. Use the Browse option to navigate to the downloaded package, select the driver and install it following the on-screen instructions. If you still have problems, I recommend you contact the support team.