1. A computer storage medium having computer-executable instructions stored thereon that when executed by a processor cause the processor to perform steps comprising: selecting a wideband set of frequency components of speech signals to form wideband speech data; selecting a narrowband set of frequency components of speech signals to form narrowband speech data, the narrowband set of frequency components including at least one of the frequency components of the wideband set of frequency components but having fewer frequency components than the wideband set of frequency components; and using the wideband speech data and the narrowband speech data to train a Hidden Markov Model that provides the likelihood of Hidden Markov Model states given speech values.