Postlingual deaf adults have a gradual defect of auditory feedback. The constantly restricted auditory feedback indicates degeneration of auditory feedback. If auditory feedback is restricted, the following phenomena occurs: First, speech perception i...
Postlingual deaf adults have a gradual defect of auditory feedback. The constantly restricted auditory feedback indicates degeneration of auditory feedback. If auditory feedback is restricted, the following phenomena occurs: First, speech perception is influenced by the restriction. According to the research on postlingual deaf adults' speech perception, they had difficulty perceiving words with little auditory information (clues) more than sentences (Liat, Riki, Yishai & Minka, 1999). As such, low speech perception ability is an important factor affecting speech production ability and speech intelligibility. Given that, it will be necessary to thoroughly research speech perception and speech production (Mi-sun Yoon․Yoon-gyeong Lee․Hyeon-seop Shim, 2000).
Secondly, the motion range of articulator reduces at the time of speech production (Harlan, Melanie & Matthies, 2007). A reduction in the motion range of articulator is closely related to neutralization of vowel at the time of vowel production. According to the research by Mi-sun Yoon and Jong-sun Kim (2000), the speech production of the hearing impaired causes the problem of articulator operation, like neutralization of tongue position, and as a result the error of vowel production occurs. Also according to the analysis of postlingual deaf adults' vowel formants, they showed the same neutralization of vowel as adults with congenital hearing impairment (Hamjavi, 1998).
There has been research that when it comes to the problems caused by the auditory feedback restriction postlingual deaf adults have, auditory feedback restoration obtained after cochlear implants leads to improving speech perception skill and closely reaching normal hearing adults' vowel production at the time of vowel production. However, there are different opinions about the time of auditory feedback restoration according to cochlear implant period. And there is few domestic research on postlingual deaf adults' speech perception and the change of their vowel production.
Therefore, this study tries to investigate postlingual deaf adults' speech perception points according to cochlear implant period and stimulus presentation condition, and their vowel formats and the area of vowel trapezium according to cochlear implant period. The study subjects are eight normal hearing adults and eight postlingual deaf adults. The postlingual deaf adults took the speech perception test with Korean standard monosyllabic word lists. And CSL was applied to both the normal hearing adults and the postlingual deaf adults to analyze F1 and F2 of the vowel formants /a/,/u/,/i/, and /ae/. Based on the difference of vowel trapezium area between the normal hearing adults and the postlingual deaf adults, this study looked into the difference of vowel trapezium area according to cochlear implant period. The study result is presented as follows: First, speech perception test points according to cochlear implant period were statistically significant. Bonferroni post-hoc analysis revealed that speech perception test points were statistically significant in all periods. In addition, speech perception test points according to stimulus presentation condition were statistically significant. In other words, with the lapse of cochlear implant period, speech perception points increased, and the points became larger when both auditory and visual stimuli (speech reading) were provided than when auditory stimulus was given.
Secondly, the postlingual deaf adults' vowel formants according to cochlear implant period were statistically significant. The low back vowel /a/ showed a rise in F1 value and a fall in F2 value, and thus tongue position was corrected low backward. The high back vowel /u/ showed drops in F1 and F2 values, and thus tongue position was corrected high backward. The high front vowel /i/ showed a drop in F1 value and a rise in F2 value, and thus tongue position was corrected high forward. The high mid vowel /ae/ didn't show any statistical significance in vowel formants between the postlingual deaf adults and the normal hearing adults.
Thirdly, the comparison analysis on the vowel trapezium area of the normal hearing adults and of the postlingual deaf adults showed that the vowel trapezium area of the normal hearing adults was larger than that of the postlingual deaf adults. It means that the postlingual deaf adults' vowels were neutralized at the time of vowel production.
Fourthly, the analysis on the vowel trapezium area of the postlingual deaf adults according to cochlear implant period showed that the difference of their vowel trapezium area according to cochlear implant period was statistically significant. Bonferroni post-hoc analysis presented that the difference between prior to cochlear implant period and one month after cochlear implant period and the difference between prior to cochlear- implant period and three month after cochlear implant period were statistically significant. It was found that with the lapse of cochlear implant period, the area of vowel trapezium became larger. It means that the postlingual deaf adults' auditory feedback restoration after cochlear implant surgery leads to closely reaching the normal hearing adults' vowel production
The study result indicates the importance of speech perception evaluation one month after cochlear implants of postlingual deaf adults. It is considered that it is important to help postlingual deaf adults produce well-resonated vowel sounds through proper and stable location of longue at the time of intervening in articulation therapy.
，韩语毕业论文，韩语论文 |
