1. A speech recognition system for identifying words from a digital input signal, the system comprising: a feature extractor for extracting at least one feature from the digital input signal; a lexicon comprising at least one noise entry; a search engine capable of identifying a sequence of hypothesis terms based on at least one feature and at least one speech model, at least one of the hypothesis terms being a noise entry found in the lexicon and at least one of the hypothesis terms being a hypothesis word; and a noise rejection module capable of replacing a hypothesis word in the sequence of hypothesis terms with a noise marker by identifying noise based in part on a model of noise phones and at least one feature.