Changes in vowel quality after cochlear implantation.

Since auditory feedback is partially restored after cochlear implantation, the aim of the present study was to investigate features of vowels, which reflect improvements in speech production. Ten postlingually deafened subjects (5 male/5 female) were recorded reading a German text before and 3 and 12 months after implantation, respectively. Selected vowels were analysed regarding the fundamental frequency (F(0)), the formant frequencies (F(1), F(2), F(3)) and the vowel space (difference between F(1) and F(2) in hertz). The F(0) decreased only descriptively after 3 and 12 months, respectively. F(1) of the vowel /e/ was significantly lower after 12 months (411 +/- 20 compared to 349 +/- 25 Hz, p < or = 0.05) and for /o/ after 3 months (446 +/- 29 compared to 408 +/- 31 Hz, p < or = 0.05) for the male patients: their vowel space also expanded significantly for the vowel /o/ (372 +/- 37 compared to 467 +/- 32 Hz, p < or = 0.05) after 12 months. Regained auditory feedback after cochlear implantation had an effect on the improvement of the production of vowels.

Characteristics of fricatives and sentence duration after cochlear implantation.

Ten postlingually deafened patients (5 male, 5 female) were examined after cochlear implantation to measure improvements in their quality of speech. Parameters such as the spectral maximum of fricatives and the duration of utterances were analysed in speech recordings taken at regular intervals after implantation. The speech samples were recorded in an audiological chamber. Parameters were analysed using ST(x) (S-Tools Software). Frequency analyses based on the fast Fourier transform and spectral estimation methods, as well as fundamental frequency and formant extraction (cepstrum, LPC = linear prediction coding) and digital filter implementations were prepared. The results indicate a tendency towards improvement in the spectral maximum of the fricatives and affricates and a shortening of the duration of the fricative parts in affricates and of sentences in nearly all our subjects. These results showed the restored auditory feedback produced by cochlear implantation to have a favourable effect on speech production.