This study is an acoustic investigation of the acquisition of vowel duration in children speaking American English. The primary goal was to find out when and how children begin to produce different vowel durations as a function of postvocalic voicing. A total of 803 longitudinal data extracted from the Providence Corpus were analyzed. The age range covered by the data was from 0;11 to 4;0. The findings are summarized as follows: (1) Children control the vowel duration conditioned by voicing before the age of 2. (2) They also make the durational distinction between the tense and lax vowels before the age of 2. (3) There is no developmental trend in the acquisition of the vowel duration conditioned by postvocalic voicing. The results suggest that children thoroughly learn the phonetic implementation of temporal parameter from the very early stage of speech production to such an extent as to make it appear as an automatic process.
Bibliographic reference. Ko, Eon-Suk (2007): "Acquisition of vowel duration in children speaking american English", In INTERSPEECH-2007, 1881-1884.