In the Windows operating systems, the sound mixer shows devices and applications. You can mute certain applications, or change their volume separately. Is there a graphical program for KDE that does this? Even a command-line interface to do this. I use ALSA sound system, no idea why that should matter, but just incase :).
For this you need to have PulseAudio installed and set as audio system. And then KMix can be compiled with support for PA and it will show controls for each playback/recording stream.