You have two audio devices, a Realtek and an Nvidia one. I suppose the Nvidia is from your video card through the HDMI connector. If you don't use HDMI for sound, disable the Nvidia sound in your Device Manager and uninstall the sound driver for it. It can be tricky, try which way it works.
Despite to whether you uninstall any audio device or not, set the one you're using as default and make sure it's chosen either as "windows default" or by name in every program you need sound in.