Progression in vowel production: comparing deaf and hearing children

An interesting but so far neglected topic in the development of infant sound production is the hypothesized progression toward adult vowel quality. Likely, this process is quite different for normally hearing babies and for deaf babies. A band filtering analysis method is used to measure the spectral envelope in these high-pitched infants'sounds automatically. The audio material of 5 hearing and 5 deaf babies is collected monthly between the 5th and 17th month, with an additional recording at 24 months. From each recording 50 randomly chosen utterances are digitized. In a PRAAT script criteria are set with regard to sound quality and F0. The utterances are then analyzed resulting in spectral envelopes wherein the dependence on F0 is minimized. Via a Principal Component Analysis a 2 - dimensional reference vowel space of all the hearing children at 24 months is determined in which individual data are projected. Preliminary results indicate that differences are found when comparing the 5th and the 24th months of hearing and deaf children.