Effects of hearing loss on vocal fold vibrations: an electroglottographic analysis

Pre-lingually hearing impaired persons have abnormal pattern of vocal fold vibration and electroglottography has been used to qualitatively describe these anomalies. However quantitative parameterization using the contact quotient and contact index lacks in literature and necessitates the present study. Three groups of moderately severe, severe and profound pre-lingual hearing impaired children were subjected to Electroglottographic analysis by vowel prolongation and the derived contact quotient and contact index data were compared with that of a control group. Results demonstrated statistically significant deviancies of contact quotient and contact index with increasing hearing loss. It was concluded that improper acoustic feedback in hearing impaired leads to a vibratory cycle with a longer than normal and more symmetrical closed phase leading to a breathy, creaky, falsetto voice with little adduction, which increases with increasing hearing loss. The study highlighted the importance of contact quotient and contact index in both evaluative and therapeutic domains.