1. A system for reducing errors in speech processing, comprising: an automatic speech recognition module configured to: receive an utterance; and generate an input word lattice based on the utterance; an electronic data store in communication with the automatic speech recognition module, the electronic data store configured to store the input word lattice, a grammar and a phoneme confusion table, wherein the input word lattice comprises a plurality of speech recognition hypotheses, the grammar comprises a plurality of commands and the phoneme confusion table comprises a plurality of insertion, deletion and substitution probabilities; and a natural language understanding module in communication with the electronic data store, the natural language understanding module configured to: generate an input finite state transducer (FST) based at least in part on the input word lattice, wherein the input FST comprises sequences of phonemes organized into input FST paths, and wherein a path of the input FST paths corresponds with a speech recognition hypothesis of the speech recognition hypotheses; generate an edit FST based at least in part on the phoneme confusion table; generate a grammar FST based at least in part on the grammar, wherein the grammar FST comprises sequences of phonemes organized into grammar FST paths, and wherein a path of the grammar FST paths corresponds to a command of the plurality of commands; generate an output FST using the input FST, the edit FST and the grammar FST, wherein a path of the output FST corresponds to a command of the plurality of commands, and wherein a first path of the output FST is indicative of a difference between a first path of the input FST paths and a first path of the grammar FST paths; compute a first difference score using the first path of the output FST; determine a command representative of the received utterance based at least in part on the first difference score; and initiate an action based at least in part on the determined command.