Aerodynamic and acoustic characteristics of a speaker with turbulent nasal emission: a case report

Aerodynamic and acoustic characteristics were determined from the speech of an adult female with mild mental retardation and severe velopharyngeal inadequacy. The speaker's productions of /s/ were characterized by consistent nasal grimacing and turbulent air emission. Aerodynamic assessment estimated the size of the velopharyngeal orifice to exceed 200 mm2 during plosive production. Nasal cross-sectional area was estimated to be 35 mm2 during quiet breathing. Nasometric evaluation indicated nasalance of 63% associated with the "Zoo" passage. Acoustic analysis of the separately recorded oral and nasal speech signals indicated spectral energies in the region of approximately 2.5 to 7.0 kHz associated with nasal emission during /s/ production. The occurrence of these frequencies suggested an acoustic/perceptual function of the nasal grimace. Pressure-flow evidence also suggested that the nasal grimace, perhaps with lingual assistance, functioned to enhance speech aerodynamics.