Some of voice characteristics of deaf people differ considerably from those with normal hearing. After cochlear implantation, auditory control of voice production is possible and quality of voice is improved.
The aim of this study was to investigate changes in some of voice parameters in deaf children after cochlear implantation.
Thirty prelingually deafened children implanted unilaterally at the age of 3-6 years were included in the study. For all of the children an acoustic analysis of Arabic vowel /æ/ was performed before cochlear implantation, 6, and 12 months after the implantation. Fundamental frequency (f0), jitter, shimmer and noise-to-harmonic ratio (NHR) were compared before and after implantation. Results of acoustic analyses were compared for children who were implanted before or at the age of 4 years and children who were implanted after the age of 4 years.
After cochlear implantation fundamental frequency did not change significantly. However, an improvement was noticed in measurements of jitter (p = 0.006) and shimmer (p = 0.021) as early as 6 months after the implantation. The noise-to-harmonic ratio improved (p = 0.010) 12 months after implantation. The children implanted before or at the age of 4 years showed a significant improvement in jitter (p = 0.003) and shimmer (p = 0.004) as early as 6 months noise-to harmonic ratio (p = 0.021) 12 months after implantation. In children implanted after the age of 4 years the significant changes was detected in f0 (p = 0.045), 12 months after the implantation and in Shimmer (p = 0.017), also 12 months after the implantation.
The results of the present study have confirmed that cochlear implantation enables auditory moment-to-moment control of pitch and loudness. The determination of jitter and shimmer in the vowel Arabic /æ/ sample proved to be a good and early indicator of improved phonation control, even in young children. The deaf children who were implanted before the age of 4 years improved their voice quality and control more quickly and to a greater extent than the children implanted after the age of 4 years.