Where the phonemes are: Dealing with ambiguity in acoustic-phonetic recognition

Errors in acoustic-phonetic recognition occur not only because of the limited scope of the recognition algorithm, but also because certain ambiguities are inherent in analyzing the speech signal. Examples of such ambiguities in segmentation and labeling (feature extraction) are given. In order to allow for these phenomena and to deal effectively with acoustic recognition errors, we have devised a lattice representation of the segmentation which allows for multiple choices that can be sorted out by higher level processes. A description of the current acoustic-phonetic recognition program in the Bolt Beranek and Newman (BBN) Speech Understanding System is given, along with a specification of the parameters used in the recognition.