1. A method of training an acoustic model, the method comprising: using values in a first set of training vectors that represent all of the frequency components in a set of frequency components and using values in a second set of training vectors that represent fewer than all of the frequency components in the set of frequency components to train a set of spectral domain acoustic model parameters ; and converting the set of spectral domain acoustic model parameters into a set of cepstral domain acoustic model parameters 326 .