One thing I've noticed when you get a TV broadcast that has 5-channel sound, it that you get the voices on the center channel. Particularly with things like voice-overs, sportscasters etc. If you can mute the center channel, you can watch a game, for example, with no commentators.
But sometimes you do want to hear what they said, if there is something on the field you don't understand. If you have a PVR, you can rewind and turn on the center channel audio (though rarely is there a good UI to do this) but here's another idea.