1. A computer-implemented method, comprising: a. aligning an utterance from a set of training data with a corresponding original transcription from the set of training data to produce a time-aligned transcription with time alignment information for each word in the utterance, wherein the set of training data includes transcription errors; b. decoding the same utterance with an incremental acoustic model and an incremental language model to produce a decoded transcription with time alignment information for each word; c. aligning the time-aligned and decoded transcriptions according to time alignment information; d. selecting all segments from the utterance having at least Q contiguous matching aligned words, where Q is a positive integer; and e. training the incremental acoustic model with the selected segments.