aThe Effect of Mandibular Disorder on the Production of Vulnerable Consonant Sounds in Children

Abstract

This exploratory case study examines the association between mandibular disorder, defined as irregular movement of the lower jaw, and the acoustic production of vulnerable consonant sounds (/s/, /z/, /ʒ/, /ʤ/, /g/, /d/, /l/, and /n/). These consonants were selected on the grounds that their production depends highly on oral cavity configuration and tongue positioning; excessive or uneven movement of the mandible is hypothesized to disrupt their accurate articulations. Eleven Kurdish-speaking children aged between 10 and 13 years were purposively selected for inclusion in the study. All participants had been diagnosed with unstable mandibular movements by an orthodontic specialist, and were divided into two subgroups: Six participants presenting with mandibular deviation and five had mandibular deflection. Data were collected via recording the children’s voice while producing individual sounds and short syllables containing the target sounds. The recordings were subsequently analyzed acoustically using the Praat sound analysis software programme. Findings indicate a clear association between mandibular disorder and inaccuracies in the production of vulnerable sounds, particularly in duration and spectral peak features. The results also revealed that the effects of mandibular disorder were much greater on the fricative consonants /z/, /s/, and /Ӡ/ relative to the other target sounds. Although the association was evident between both groups of mandibular disorder and misproduction of target sounds, the total mean variations of the acoustic parameters between the deviation and deflection groups did not reach statistical significance.

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