Evaluation of the Presence of Subharmonics in the Phonation of Children with Smith Magenis Syndrome

Smith-Magenis syndrome SMS is a rare disease relatively unknown and underdiagnosed. This genetic disorder involves among others, neurodevelopmental deficits, which affect the complex mechanisms implicated in the production of speech. In this way, all levels of speech production are impacted. Individuals diagnosed with SMS present a deep, hoarse voice, dysphonia, excess of vocal muscle stiffness, disfluencies, tachylalia, high unintelligibility. This study investigates the origin of one of these characteristics (deep, hoarse voice) and compares de voice of a group of children with SMS (N = 12) with a healthy normative control group of children (N = 12) matched in age and gender. To observe the possible effects of age and gender, four groups were considered: boys and girls, both genders divided in two groups of age: 5 to 7 years old, and 8 to 12 years old. As the study is centred in the cause of the characteristic deep, hoarse voice of patients with SMS, acoustic analysis of a sustained vowel /a/ was performed, thus avoiding coarticulation effects. The present study is based in the search of subharmonic components of voice in the cepstrum domain that may explain that characteristic of SMS voices.