Spontaneus speech (approx.10 hours) produced by ten deaf children (5 males and 5 females, mean age 5 years old, with severe sensory-neural hearing impairment) was recorded during rehabilitation sessions and some selected parts were analyzed by means of a KAY 5500 DSP-Sonagraph. Many phonetic measurements were performed on this speech material (mean vowel formant values, forma/it transition patterns, power spectrum of stationary unvoiced consonants, prosodic parameters), but particular attention was paid to pitch and timing control. All measurements were compared with an analogous set of data obtained from a control group of ten normal children of the same mean age.

Fundamental frequency and peak intensity values were measured for each period and on this base temporal patterns were drawn and jitter and shimmer histograms were calculated for both groups; furthermore, global word duration, stressed vowel duration, and silent pauses were measured in order to evaluate the performances of deaf children in controlling timing parameters of speech. The results show that while the vowel production seems to underlie a sort of cathegorization, pitch and timing control definitely need auditory feedback.