Vocal Characteristics in Adults with Down Syndrome
Adults with Down Syndrome (DS) often present with the same types of anatomical and vocal features as children. In their article "Speech Impairment in Down Syndrome: A Review" (2013), Ray D. Kent and Houri K. Vouperian review the existing literature on vocal characteristics of individuals with DS. Their findings indicate the following vocal issues may be present in adults:
Increased levels of perturbation
Vocal hyperfunction
Resonance disorders
Higher fundamental frequency
Reference:
Kent, R. D., Vouperian, H. K., (2013). Speech impairment in Down Syndrome: A review.Journal of Speech, Language & Hearing Research, 56(1), 178-210. doi:10.1044/1092-4388(2012/12-0148)
Increased levels of perturbation
- Adults with Down Syndrome have generally been found to exhibit greater perturbation in both amplitude (shimmer) and frequency (jitter)
- These perturbations could be the result of neurological, structural, aerodynamic, or resonatory characteristics
Vocal hyperfunction
- Since many adults with DS present with muscle weakness (hypotonia), their laryngeal muscles need to exert more energy to initiate and sustain phonation
- Individuals with DS may also lose acoustic energy due to hypernasality, thus forcing their vocal folds to work harder to vibrate
Resonance disorders
- Abnormalities in the nasal cavities, sinuses, and tissue divisions between the oral and nasal cavities may contribute to an abnormal balance between oral and nasal resonance, resulting in hypernasality.
Higher fundamental frequency
- One difference between the presentation of adults and children with DS is that while children typically have a lower than average fundamental frequency, adults with DS tend to have a higher fundamental frequency
- Higher FO could be due to a number of factors, including smaller body size and smaller relative laryngeal size
Reference:
Kent, R. D., Vouperian, H. K., (2013). Speech impairment in Down Syndrome: A review.Journal of Speech, Language & Hearing Research, 56(1), 178-210. doi:10.1044/1092-4388(2012/12-0148)