Air Pressure Responses to Sudden Vocal Tract Pressure Bleeds During Production of Stop Consonants New Evidence of Aeromechanical Regulation Research Article
Research Article  |   August 01, 2004
Air Pressure Responses to Sudden Vocal Tract Pressure Bleeds During Production of Stop Consonants
 
Author Affiliations & Notes
  • David J. Zajac
    University of North Carolina at Chapel Hill
  • Mark C. Weissler
    University of North Carolina at Chapel Hill
Article Information
Speech, Voice & Prosodic Disorders / Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   August 01, 2004
Air Pressure Responses to Sudden Vocal Tract Pressure Bleeds During Production of Stop Consonants
Journal of Speech, Language, and Hearing Research, August 2004, Vol. 47, 784-801. doi:10.1044/1092-4388(2004/059)
History: Received November 11, 2003 , Accepted February 11, 2004
 
Journal of Speech, Language, and Hearing Research, August 2004, Vol. 47, 784-801. doi:10.1044/1092-4388(2004/059)
History: Received November 11, 2003; Accepted February 11, 2004
Web of Science® Times Cited: 2

Two studies were conducted to evaluate short-latency vocal tract air pressure responses to sudden pressure bleeds during production of voiceless bilabial stop consonants. It was hypothesized that the occurrence of respiratory reflexes would be indicated by distinct patterns of responses as a function of bleed magnitude. In Study 1, 19 adults produced syllable trains of /pʌ/ using a mouthpiece coupled to a computer-controlled perturbator. The device randomly created bleed apertures that ranged from 0 to 40 mm2 during production of the 2nd or 4th syllable of an utterance. Although peak oral air pressure dropped in a linear manner across bleed apertures, it averaged 2 to 3 cm H2O at the largest bleed. While slope of oral pressure also decreased in a linear trend, duration of the oral pressure pulse remained relatively constant. The patterns suggest that respiratory reflexes, if present, have little effect on oral air pressure levels. In Study 2, both oral and subglottal air pressure responses were monitored in 2 adults while bleed apertures of 20 and 40 mm2 were randomly created. For 1 participant, peak oral air pressure dropped across bleed apertures, as in Study 1. Subglottal air pressure and slope, however, remained relatively stable. These patterns provide some support for the occurrence of respiratory reflexes to regulate subglottal air pressure. Overall, the studies indicate that the inherent physiologic processes of the respiratory system, which may involve reflexes, and passive aeromechanical resistance of the upper airway are capable of developing oral air pressure in the face of substantial pressure bleeds. Implications for understanding speech production and the characteristics of individuals with velopharyngeal dysfunction are discussed.

KEY WORDS: stop consonants, oral air pressure, subglottal air pressure, respiratory reflexes, velopharyngeal dysfunction

Acknowledgments
This work was supported by National Institute of Dental and Craniofacial Research Grant R01 DE-10175. We would like to thank Richard Lutz and Olivier Monbureau, for their invaluable assistance with the development and programming of the pressure perturbator, and Ashlie Flack, for help with data collection and analysis. We are indebted to Donald Warren for his insights into cleft palate speech production.
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