The influence of cochlear implantation on some voice parameters

Abstract

Some of the voice characteristics of deaf people differ considerably from those of speakers with normal hearing. After a cochlear implantation, auditory control of voice production is possible and the quality of the voice is improved. The aim of this study was to investigate the changes in some of the voice parameters in deaf children after cochlear implantation. Thirty-one prelingually deafened children implanted unilaterally at the age of 2.5-13 years were included in the study. For all of the children an acoustic analysis (Multi-Dimensional Voice Program, Kay Elemetrics Corp., USA) of the Slovene vowel 'a' was performed before cochlear implantation and 6, 12 and 24 months after the implantation. The fundamental frequency (F0), jitter, shimmer and noise-to-harmonic ratio (NHR) were compared before and after the implantation. The results of the acoustic analyses were compared for the children who were implanted before or at the age of 4 years and the children who were implanted after the age of 4 years. After the cochlear implantation the fundamental frequency did not change significantly. However, an improvement was noticed in the 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=0.013) 24 months after the 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 and in noise-to-harmonic ratio (p=0.021) 12 months after the implantation. In the children implanted after the age of 4 years the only significant change was detected in F0 (p=0.045), 12 months after the implantation, and in Shimmer (p=0.017), 24 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 'a' 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 control more quickly and to a greater extent than the children implanted after the age of 4 years.