An information-theoretic analysis of developmental changes in speech

Developmental changes in the human speech production system signal age-dependent variability in the speech signal properties. In this paper, an information-theoretic analysis of developmental changes in the speech signal is presented. The effects of age and signal bandwidth on speech signal features are analyzed especially motivated by implications to automatic recognition of children's speech. Mutual information is calculated between cepstral features and the vowel phonetic class for different age groups and signal bandwidths. The results show that information contained in cepstral features about phonetic classes increases as bandwidth increases for all ages. Cepstral features of adult speech convey more information compared to that of children's speech for both genders. Information increases rapidly between bandwidths 500 Hz and 4500 Hz. These findings based on mutual information correspond well with vowel recognition (classification) experiments. The vowel recognition experiment shows that as bandwidth increases recognition accuracy increases as well.