25. A system for of assessing a key child's language development, comprising: a processor-based device executing software comprising: an application having an audio engine configured to process an audio recording taken in the key child's language environment to identify segments of the recording that correspond to the key child's vocalizations; an adult automatic speech recognition phone decoder configured to process segments that correspond to a key child's vocalizations to identify each occurrence of each of a plurality of phone categories, wherein each of the phone categories corresponds to a pre-defined speech sound; and an expressive language assessment component configured to determine a distribution for the phone categories and using the distributions in an age-based model to assess the key child's expressive language development, wherein the age-based model is selected based on the key child's chronological age and the age-based model includes a weight associated with each of the phone categories.
25. A system for of assessing a key child's language development, comprising: a processor-based device executing software comprising: an application having an audio engine configured to process an audio recording taken in the key child's language environment to identify segments of the recording that correspond to the key child's vocalizations; an adult automatic speech recognition phone decoder configured to process segments that correspond to a key child's vocalizations to identify each occurrence of each of a plurality of phone categories, wherein each of the phone categories corresponds to a pre-defined speech sound; and an expressive language assessment component configured to determine a distribution for the phone categories and using the distributions in an age-based model to assess the key child's expressive language development, wherein the age-based model is selected based on the key child's chronological age and the age-based model includes a weight associated with each of the phone categories. 27. The system of claim 25 , wherein the expressive language assessment component determines a frequency distribution.