Secretion Bubbling as the Sound Mechanism for Nasal Rustle: A Perceptual Study

Area of Science:

• Speech-language pathology
• Acoustic analysis
• Aerodynamics

Background:

• Secretion bubbling at the velopharyngeal (VP) valve is associated with small VP openings during oral pressure consonant production.
• High-speed nasopharyngoscopy reveals a correlation between bubbling frequency and nasal acoustic measurements.

Purpose of the Study:

• To determine if the sound from secretion bubbling is perceived as nasal rustle (nasal turbulence).

Main Methods:

• Speech samples from pediatric patients diagnosed with nasal rustle were analyzed.
• A custom filter removed sounds from secretion bubbling.
• Listeners rated nasal rustle perception before and after filtering.

Main Results:

• Filtering secretion bubbling sound reduced nasal rustle perception across all cases.
• Nasal rustle perception was eliminated in 40% of the speech samples.
• Listener reliability for nasal rustle perception was excellent pre-filtering and moderate-to-good post-filtering.

Conclusions:

• Spectral filtering based on bubbling frequencies supports the hypothesis that turbulent airflow interacting with secretion bubbling generates nasal sound.
• This finding has implications for understanding and managing nasal rustle in speech.