14. The computer-readable medium of claim 9 , further comprising iteratively using the probability of the observed value corresponding to the hidden trajectory value for a plurality of observed values and hidden trajectory values to train a speech recognition model, and using the speech recognition model to interpret a speech input and provide an output based at least in part on the interpretation of the speech input.
9. A computer-readable medium having computer-executable instructions which, when executed by a computing device with a processor, enable the computing device to receive, at the processor, a speech signal and use time-ordered differences in observation trajectory cepstra derived from the speech signal by the processor and time-ordered differences in vocal tract resonance trajectory cepstra derived from the speech signal by the processor to evaluate, with the processor, a probability of an observed value corresponding to a hidden trajectory valuer by evaluating a parameter-free, non-linear prediction function acting on the time-ordered differences in vocal tract resonance trajectory cepstra, and using the prediction function to evaluate a probability of the observed value corresponding to the hidden trajectory value and to output an interpretation of the speech signal based on the probability of the observed value.