Unwanted sound output

I recently installed a program called WiDisplay to use my iPad 2 as a secondary display for my MacBook Pro. Later I decided it wouldn't work and ran the uninstaller. After a while, I went to the Sound pane in System Preferences, and there was an option called WiDisplay Loopback Device in both the Input and Output panels. Any ideas how to remove them? They're not really doing anything (except annoying me) 👿 so it's not urgent. But any help here would be much appreciated.