This study has a central goal of unifying a currently diverse group of voice therapy approaches used around the world. With different names, different origins, and different protocols, they appear at first glance to have little in common. Close scrutiny, however, reveals that all of them utilize exercises with a semi-occluded vocal tract. These semi-occlusions are in the form of voiced fricatives, lip and tongue trills, nasal consonants, tense vowels /u/ and /o/, and flow-resistant tubes inserted into the mouth. The benefits derived from exercising with a semi-occluded vocal tract have recently been demonstrated scientifically. One benefit is a steady supraglottal pressure to counteract a tendency to hyper-adduct or "press" the vocal folds for loudness and accent in speech. Another benefit is favorable acoustic impedance above the glottis for low phonation threshold pressure and "ease of phonation." To gain control over the pressure-flow characteristics of the semi- occlusions, a series of tubes and non-tube articulatory gestures will be studied and optimized for a therapy protocol.
Specific aims are to (1) characterize and rank-order vocal tract semi-occlusions (lip trills, tongue, trills, humming, voiced fricatives, tube phonation) in terms of an ral pressure to subglottal pressure ratio, primary methodologies being oral pressure manometry and electroglottography (EGG), (2) to determine the steady pressure-flow characteristics and acoustic input impedance of selected tubes with different diameters and lengths, (3) to assess the degree to which mixed register (with moderate vocal fold contact) is achievable with tube phonation, and to determine if mixed register has the lowest phonation threshold pressure;results will be achieved by comparing measured EGG to computer simulated contact area and maximum power transfer to the vocal tract, (4) to quantify epilaryngeal changes as a function of oral semi-occlusion with the primary instrumentation being magnetic resonance imaging (MRI) with a select group of subjects, (5) to conduct a superiority trial between non-speech semi-occluded exercises (tube phonation) and progressive Lessac-Madsen Resonant Voice Therapy (LMRVT) in terms of clinical economy and patient adherence.
People who speak a lot can stress their vocal folds with vibration, collision, and pressing together the vocal folds. Stretching and un-pressing exercises can lighten this mechanical load. By phonating into a thin tube between the lips, pressure is built up inside the airway, above the vocal folds, to facilitate stretching and un- pressing. A formal study is conducted to optimize the tube dimensions and administer two therapy protocols to determine superiority in terms of clinical economy (time spent in instruction and practice).