20. The tangible, non-transitory computer-readable storage medium of claim 17 , wherein each of the HMMs in the plurality is associated with a respective elemental speech unit, and has one or more states corresponding to one or more temporal phases of the associated, respective elemental speech unit, wherein the multiplicity of states comprises a collection of the one or more states of each of the HMMs in the plurality, and wherein determining the speech content corresponding to the sequence of temporal frames of the audio input signal comprises determining a probable sequence of elemental speech units based on a most likely sequence of states of the multiplicity.
21. The tangible, non-transitory computer-readable storage medium of claim 20 , wherein each elemental speech unit is at least one of a phoneme, a triphone, or a quinphone.