Sometimes for games that are broadcast in 5.1 surround sound (I'm thinking HDNet hockey in particular, but it might work for CFB on ESPN or something), unplugging the front center channel took away the play-by-play, but left the ambient noise. It's worth trying, but I think it'd have to be an HD broadcast to be in 5.1.
Come to think of it, it might have been when ABC had Monday Night Football.