For children with hearing impairment, limited access to acoustic information causes different types of problems when acquiring speech abilities (Serry and Blamey 1999). Factors such as degrees of hearing loss, types of hearing aids, and experiences with hearing aids and educational training programs, etc. have been reported to play a role in speech acquisition (Geers et al. 2003, Mildner et al. 2006, Nittrouer and Burton 2003, Robbins et al. 2004, Svirsky et al. 2004, Wie et al. 2007). Comparative analyses of speech data produced by hearing and hard of hearing children are often conducted to specify the types of difficulties, in which quantitative measures are designed to empirically evaluate different linguistic and developmental aspects of spoken language use. For instance, mean length of utterance in morphemes (MLU), grammatical complexity and lexical diversity were used to differentiate spoken language performance between hearing children and children with specific language impairment (Brown 1973, Malvern and Richards 2002, Klee and Fitzgerald 1985, Klee et al. 2004, McLaughlin and Cullinan 1989, Miller and Chapman 1981). Operating these indicators requires well-defined and precisely identified morpheme units in the particular language to calculate the type-token ratio. This kind of data processing method is theoretically complex, and requires professional, linguistic expert judgements. Nevertheless, Klee and Fitzgerald (1985) have concluded that not all results of MLU have proven a significant relationship with age or grammatical development.