4. The method of claim 3 , further comprising: aligning frames of the original waveform and frames of each synthetic waveform to a corresponding one of the N textual transcriptions; and calculating the distance measure between the original waveform and each of the synthetic waveforms based on the corresponding alignments.
4. The method of claim 3 , further comprising: aligning frames of the original waveform and frames of each synthetic waveform to a corresponding one of the N textual transcriptions; and calculating the distance measure between the original waveform and each of the synthetic waveforms based on the corresponding alignments. 5. The method of claim 4 , further comprising: retrieving feature vectors corresponding to the original waveform; and generating feature vectors for each synthetic waveform such that the feature vectors for the synthetic waveforms are-similar in structure to the feature vectors of the original waveform, wherein the alignment is performed by time-aligning the feature vectors of the original waveform and the feature vectors of each synthetic waveform with the corresponding one of the N textual transcriptions.