title: Characterization of Flow-resistant Tubes Used for Semi-occluded Vocal Tract Voice Training and Therapy.
abstract: OBJECTIVE
  This study aimed to characterize the pressure-flow relationship of tubes used for semi-occluded vocal tract voice training/therapy, as well as to answer these major questions: (1) What is the relative importance of tube length to tube diameter? (2) What is the range of oral pressures achieved with tubes at phonation flow rates? (3) Does mouth configuration behind the tubes matter?
  
  
  METHODS
  Plastic tubes of various diameters and lengths were mounted in line with an upstream pipe, and the pressure drop across each tube was measured at stepwise increments in flow rate. Basic flow theory and modified flow theory equations were used to describe the pressure-flow relationship of the tubes based on diameter and length. Additionally, the upstream pipe diameter was varied to explore how mouth shape affects tube resistance.
  
  
  RESULTS
  The modified equation provided an excellent prediction of the pressure-flow relationship across all tube sizes (6% error compared with the experimental data). Variation in upstream pipe diameter yielded up to 10% deviation in pressure for tube sizes typically used in voice training/therapy.
  
  
  CONCLUSIONS
  Using the presented equations, we can characterize resistance for any tube based on diameter, length, and flow rate. With regard to the original questions, we found that (1) For commonly used tubes, diameter is the critical variable for governing flow resistance; (2) For phonation flow rates, a range of tube dimensions produced pressures between 0 and 7.0 kPa; and (3) The mouth pressure behind the lips will vary slightly with different mouth shapes, but this effect can be considered relatively insignificant.
authors.affiliation: The National Center for Voice and Speech, The University of Utah, 136 South Main Street, Suite 320, Salt Lake City, Utah 84115. Electronic address: simeon.smith@utah.edu.
authors.forename: Simeon L
authors.initials: SL
authors.lastname: Smith
authors.affiliation: The National Center for Voice and Speech, The University of Utah, 136 South Main Street, Suite 320, Salt Lake City, Utah 84115; Department of Communication Sciences and Disorders, Wendell Johnson Speech and Hearing Center, University of Iowa, Iowa City, Iowa 52242.
authors.forename: Ingo R
authors.initials: IR
authors.lastname: Titze
mesh_terms: D000403:Airway Resistance; D004867:Equipment Design; D006801:Humans; D007830:Larynx / Q000503:physiopathology*; D008962:Models, Theoretical; D009055:Mouth / Q000503:physiopathology*; D010699:Phonation; D011312:Pressure; D012212:Rheology; D014832:Voice Disorders / Q000503:physiopathology / Q000628:therapy*; D014833:Voice Quality; D014834:Voice Training
keywords: flow resistance; flow-resistant tubes; semi-occluded vocal tract; voice therapy; voice training