The influence of the auditory prosthesis type on deaf children's voice quality

In the last years, technology has made it possible for deaf people, and especially for deaf children, to enter the world of sound and, as a consequence, to facilitate communicative competence in oral language, which used to be an insurmountable obstacle. With this article we are trying to carry out a revision of the descriptions that have traditionally featured deaf children's voice.

We analyse the voice quality obtained out of a research with 62 children (35 girls and 27 boys) with profound deafness of several degrees, aged on average 7 years 4 months, and users of different types of auditory prostheses (analogue/digital hearing aids or cochlear implants) experimental group--Voice quality was evaluated from the production of a sustained vowel /a:/ for four-five seconds, considering F(0), jitter, shimmer and NHR values.

The results are compared with the ones obtained from a control group of hearing children (n=54). The Experimental Group shows altered voice quality parameters. Particularly in F(0) (294.079 Hz) and shimmer (0.568 dB), there are statistically significant values in comparison with the control group (p<0.001). With regards to jitter (1.474%), differences were smaller. Nevertheless, the results show how the profiles reached by deaf children are nowadays more similar to those reached by the hearing control group. However, the degree of hearing impairment and the type of prosthesis used can determine the parameters of deaf children's voice quality to a great extent. Thus, the digital hearing aid users are the ones who present better voice quality values: F(0) (265.50 z); jitter (1.009%) and shimmer (0.486 dB); whereas implant users: F(0) (287.93 z); jitter (1.344%) and shimmer (0.526 dB), and particularly analogue hearing aid users: F(0) (323.80 z); jitter (1.999%) and shimmer (0.687 dB), did show significant differences in comparison with the control group of hearing children.

In the study of voice quality in children with profound hearing loss, it is very important to have information both about the degree of hearing loss and the kind of prosthesis used. Implant users show more altered voice quality than digital hearing aid users. However, the hearing loss they compensate is much more important than the hearing loss compensated by the hearing aids. Therefore, we consider that both prostheses help children with hearing loss to have a more normalized voice quality than what scientific literature has traditionally stated. Finally, we question the validity of using some acoustic parameters as indicators of voice quality in deaf children having no laryngeal problems.