Nasal rustle: An evidence-based description

Abstract

“Nasal rustle” (also known as “nasal turbulence”) is a loud nasal distortion that can be heard during speech production in certain children with velopharyngeal insufficiency (VPI). It occurs when there is a leak of airflow into the nasal cavity through a small velopharyngeal opening. While the perception of audible nasal emission—including nasal rustle—is a standard means for the diagnosis of VPI, there is no consensus on the sound generation mechanism. Current hypotheses include aerodynamic turbulence, velar flutter, and bubbling of mucus secretion. This study investigates the correlation between the acoustic signal of nasal rustle and physical movement at the superior velopharyngeal port. Several pediatric VPI patients were recorded via high-speed video nasopharyngoscopy and simultaneous nasometry during production of speech sounds susceptible to nasal rustle. Instances of perceived nasal rustle in the acoustic signal were identified and compared with the high-speed video. A high correlation was found between the bubbling frequency of mucus secretion above the velopharyngeal port and frequencies in the nasal acoustic signal, suggesting that secretion bubbling is a mechanism for generating nasal rustle. From this analysis, an integrated description of nasal rustle invoking physiological, physical, and acoustic principles is proposed.“Nasal rustle” (also known as “nasal turbulence”) is a loud nasal distortion that can be heard during speech production in certain children with velopharyngeal insufficiency (VPI). It occurs when there is a leak of airflow into the nasal cavity through a small velopharyngeal opening. While the perception of audible nasal emission—including nasal rustle—is a standard means for the diagnosis of VPI, there is no consensus on the sound generation mechanism. Current hypotheses include aerodynamic turbulence, velar flutter, and bubbling of mucus secretion. This study investigates the correlation between the acoustic signal of nasal rustle and physical movement at the superior velopharyngeal port. Several pediatric VPI patients were recorded via high-speed video nasopharyngoscopy and simultaneous nasometry during production of speech sounds susceptible to nasal rustle. Instances of perceived nasal rustle in the acoustic signal were identified and compared with the high-speed video. A high correlation was found b...