Effect of the loss of auditory feedback on segmental parameters of vowels of postlingually deafened speakers.

OBJECTIVE: The most obvious and best documented changes in speech of postlingually deafened speakers are the rate, fundamental frequency, and volume (energy). These changes are due to the lack of auditory feedback. But auditory feedback affects not only the suprasegmental parameters of speech. The aim of this study was to determine the change at the segmental level of speech in terms of vowel formants. METHODS: Twenty-three postlingually deafened and 18 normally hearing speakers were recorded reading a German text. The frequencies of the first and second formants and the vowel spaces of selected vowels in word-in-context condition were compared. RESULTS: All first formant frequencies (F1) of the postlingually deafened speakers were significantly different from those of the normally hearing people. The values of F1 were higher for the vowels /e/ (418+/-61 Hz compared with 359+/-52 Hz, P=0.006) and /o/ (459+/-58 compared with 390+/-45 Hz, P=0.0003) and lower for /a/ (765+/-115 Hz compared with 851+/-146 Hz, P=0.038). The second formant frequency (F2) only showed a significant increase for the vowel/e/(2016+/-347 Hz compared with 2279+/-250 Hz, P=0.012). The postlingually deafened people were divided into two subgroups according to duration of deafness (shorter/longer than 10 years of deafness). There was no significant difference in formant changes between the two groups. CONCLUSION: Our report demonstrated an effect of auditory feedback also on segmental features of speech of postlingually deafened people.

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.