Acoustic and Articulatory Characteristics of Malayalam Speaking Children Using Cochlear Implant

Abstract

Restoration of audition through a Cochlear Implant (CI) is established to have a significant benefit for individuals with hearing loss. Speech characteristics of children with cochlear implantation are reported to be approaching normal limits compared to children fitted with digital hearing aids. Since the phonetic or phonological characteristics vary across languages, it is important to replicate studies into other common spoken languages to provide language appropriate data for rehabilitation professionals working with CI. In the context of a highly well-executed CI scheme, ‘Shrutitharangam’ by the state government of Kerala, there is a steady increase in the number of children with hearing impairment undergoing CI surgery. Therefore, their effective speech rehabilitation plan should be on strong foundations of language appropriate evidence-based research. Further, there are no published Indian studies which provide detailed profiling of acoustics and articulatory characteristics in children using CI. The present study aimed to investigate the acoustic and articulatory characteristics of Malayalam speaking children using CI in the age range of 4 and 8 years and compare with age matched typical children. A total of 80 participants were recruited for the study. The clinical group consisted of 30 children with congenital hearing loss and were fitted CI before the age of 3 years. The participants of the clinical group were further divided into two subgroups based on the number of years of cochlear implant use. Subgroup I consisted of participants with 2-3 years of cochlear implant experience and subgroup II with 3-4 years of implant experience. The chronological age of participants in subgroup I was in the range of 4.0-5.11 years (2-3 years of CI experience) and subgroup II in the chronological age range of 6-7.11 years (3-4 years of CI experience). TDC group was also divided into two subgroups 72 of 25 participants each based on the chronological age (4.0-5.11 & 6-7.11 years).of the participants. The study consists of two major sections: 1. Acoustic analysis 2. Articulatory analysis. The test stimuli for acoustic analysis were simple picturable words and picture stimulus for Malayalam Diagnostic Articulation Test-Revised (MAT-R) was administered for articulatory analysis. Speech samples were elicited through picture-naming task and was audio recorded. The acoustic parameters considered for the study included nine temporal and four spectral parameters. For detailed articulatory profiling, vowels, consonants, and consonant clusters were analyzed quantitatively and qualitatively. The results indicated significant effect of duration of CI use in both acoustic and articulatory measures. There was no significant effect of gender in any of the parameters investigated. Most of the variables in spectral measures approached normal limits with 2-3 years of CI experience. However, temporal measures were significantly deviant from age matched peers. Interestingly, fricatives and affricates which are generally late acquiring, approached typical values in duration measures with 3-4 years of CI experience. A considerable improvement in the articulatory abilities was also noted for vowels, consonants and consonant clusters with increased duration of CI use. However, children using CI exhibited significantly lower scores for all places and manners of articulation compared to TDC. Although there was a delay in acquisition of articulatory abilities, children using CI exhibited similar trend to that of TDC. The study highlights the importance of intense articulation training for a longer duration following CI surgery to achieve intelligible speech and the need for school/ district wise availability of speech therapy.