Patent ID: 7627473

Claim:
A computer-readable storage medium having computer-executable instructions stored thereon that when executed by a processor cause the processor to perform steps comprising: receiving a speech signal; determining a sequence of observed values from the speech signal; forming a separate constrained trellis for each of a plurality of phonetic units, each constrained trellis comprising hidden states at a plurality of time points; computing a recursive score for each constrained trellis, each recursive score based on an exponential function with e raised to a sum of weighted feature function values, wherein at least one of the feature function values is set equal to a value of a formant in the speech signal based on a determination that a current hidden state matches a particular hidden state; comparing the recursive scores for the constrained trellises to each other to identify the constrained trellis that provides the greatest score; and identifying the phonetic unit associated with the constrained trellis that provides the greatest score as the phonetic unit represented by the speech signal.