1. A speech recognition system for recognizing spoken input received from a source of the spoken input coupled to the speech recognition system, the speech recognition system comprising: a. input means for receiving the spoken input from the source of the spoken input; and b. processing means coupled to the input means for performing a first pass speech recognition technique on the spoken input and for forming first pass results; wherein the processing means selectively performs a second pass speech recognition technique on the spoken input according to the first pass results, first pass results include alignments of speech and silence of the spoken input, and further wherein when the second pass speech recognition technique is performed, the second pass speech recognition technique does not process at least some portions of the spoken input which are aligned to silence.
2. The speech recognition system according to claim 1 , wherein the processing means employs a margin of silence before and after each utterance of the spoken input.