Transcription is the textual output of the speech recognition process, be it phonetic, LVCSR or direct. All current applications of them do take some context in consideration, usually via a transition matrix and lots of training data.

What I'm proposing is to pass the output of speech recognition through a binary classifier that answers the question "is this text gibberish?", which is trained with the help of a textual language model, unrelated to the speech recognition pass.