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.
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. 10. The computer-readable medium of claim 9 , further comprising using the vocal tract resonance trajectory cepstra and the time-ordered differences in the vocal tract resonance trajectory cepstra to estimate a plurality of target vocal tract resonance vector parameters.