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, by: including a silence in a selected segment comprising the Q matching aligned words when the selected segment is preceded or followed by a silence; and when there is no silence preceding or succeeding the selected segment: selecting the selected segment according to the original transcription with time alignment information; and inserting part of a silence segment from the beginning of the utterance into the beginning of the selected segment, and appending a part of a silence segment from the beginning of the utterance to the end of the selected segment; e. training the incremental acoustic model with the selected segments; and f. evaluating the accuracy of the incremental acoustic model built from the training data including transcription errors compared to the accuracy of an acoustic model built from a similar amount of training data having no transcription errors.