Effects of Straw Phonation Through Tubes of Varied Lengths on Sustained Vowels in Normal-Voiced Participants.

OBJECTIVE: To examine the immediate effects of straw phonation exercises in normal subjects while altering the effective length of the vocal tract. STUDY DESIGN: A nonrandomized comparison of semi-occluded vocal tract length during straw phonation exercises was carried out. METHODS: Oral pressure, mean airflow, aerodynamic resistance, and contact quotient were measured in 20 healthy subjects immediately before and after straw phonation exercises. A short- and long-duration phonatory task was used to examine the voice parameters during semi-occluded vocal tract exercises. These tasks involved repeating a vocalization of the vowel /a/ through a tube. Each subject underwent the protocol using tubes of three different lengths (7.5 cm, 15 cm, and 30 cm) to allow for the effect of moving the outlet of the vocal tract distal to the mouth to be monitored. RESULTS: Oral pressure and aerodynamic resistance decreased significantly, contact quotient showed a decreasing trend, and airflow increased significantly in pre- and postmeasurements 15 minutes after a long-duration phonatory task. Short-duration tasks were found to have no effect on voice parameters. CONCLUSION: The results present and validate a method to isolate the effect that the length of a semi-occluded vocal tract has during straw phonation exercises.

Parameters From the Complete Phonatory Range of an Excised Rabbit Larynx.

OBJECTIVE: This study aims to collect data throughout the complete phonatory range using rabbit larynges. STUDY DESIGN: This is a methodological excised rabbit larynx study. METHODS: Seven rabbit larynges were dissected and mounted on a modified excised laryngeal apparatus. Phonation was initiated at phonation threshold pressure (PTP) and airflow was increased by consistent increments until phonation instability pressure (PIP) was reached. At each airflow level, aerodynamic measurements, acoustic recordings, and high-speed videos were recorded. This procedure was repeated at multiple elongation conditions to further explore the parameters. Data were then compared across subjects and elongation conditions. RESULTS: At PTP, subglottal pressure, fundamental frequency, and sound pressure level were found to increase significantly as elongation was increased. As elongation was increased at PIP, airflow was found to significantly decrease, whereas fundamental frequency was found to significantly increase. Vibratory amplitude decreased at both PTP and PIP as elongation increased. Also, as elongation increased, the range of all parameters was found to decrease significantly. CONCLUSIONS: The results obtained, combined with the similarities of the histologic structure of the vocal fold lamina propria between rabbits and humans, validate the rabbit larynx as an effective and reliable model for tissue inflammation studies.

Evaluation of an asymmetric anterior glottic web in an excised canine larynx model.

The main objective of the study is to model asymmetry within anterior glottic webs in excised larynges using sutures and apply aerodynamic and acoustic analyses. Anterior glottic webs (AGW) were modeled in eight excised larynges using sutures secured at the level of the glottis to mimic the scar tissue of the web. Each of the eight larynges were tested under three different pressure increments for each of the three models of AGW: symmetric, vertically asymmetric, and laterally asymmetric. Phonation threshold pressure (PTP) and flow (PTF) differed significantly across AGW conditions (p = 0.006 and p = 0.005, respectively). Additionally, vocal efficiency was significantly different among conditions (p = 0.005) as well as significantly lower in the asymmetric groups (p = 0.015 and p = 0.007). Perturbation measures were not significantly different across conditions. Correlation dimension (D2) was significantly different at PTP, 1.25 × PTP, and 1.5 × PTP (p = 0.003, p = 0.010, and p < 0.001, respectively) as well as significantly higher in the asymmetric groups at each pressure increment. The increased PTP, PTF, and D2 values as well as decreased vocal efficiency among the asymmetric conditions indicates a significant decrease in vocal function, and thus represents that asymmetries could be a contributing factor to the pathological symptoms associated with glottic webs.

Validation and Evaluation of the Effects of Semi-Occluded Face Mask Straw Phonation Therapy Methods on Aerodynamic Parameters in Comparison to Traditional Methods.

OBJECTIVES/HYPOTHESIS: Traditional semi-occluded vocal tract therapies have the benefit of improving vocal economy but, do not allow for connected speech during rehabilitation. In this study, we introduce a semi-occluded face mask (SOFM) as an improvement upon current methods. This novel technique allows for normal speech production, and will make the transition to everyday speech more natural. We hypothesize that use of an SOFM will lead to the same gains in vocal economy seen in traditional methods. STUDY DESIGN: Repeated measures excised canine larynx bench experiment with each larynx subject to controls and a randomized series of experimental conditions. METHODS: Aerodynamic data were collected for 30 excised canine larynges. The larynges were subjected to conditions including a control, two tube extensions (15 and 30 cm), and two tube diameters (6.5 and 17 mm) both with and without the SOFM. Results were compared between groups and between conditions within each group. RESULTS: No significant differences were found between the phonation threshold pressure and phonation threshold flow measurements obtained with or without the SOFM throughout all extension and constriction levels. Significant differences in phonation threshold pressure and phonation threshold flow were observed when varying the tube diameter while the same comparison for varying the tube length at least trended toward significance. CONCLUSIONS: This study suggests that a SOFM can be used to elicit the same gains in vocal economy as what has been seen with traditional semi-occluded vocal tract methods. Future studies should test this novel technique in human subjects to validate its use in a clinical setting.

Quantitative Study of the Effects of Dehydration on the Viscoelastic Parameters in the Vocal Fold Mucosa.

OBJECTIVES: The goal of this study was to quantify the viscoelastic parameters of the vocal fold mucosa at varying dehydration levels. STUDY DESIGN AND METHODS: Healthy canine larynges were obtained postmortem, and the samples were separated from the subglottal wall. The samples were dehydrated in a vacuum dryer. According to the total dehydration time per sample, dehydration levels were divided into four degrees: 0%, 40%, 60%, and 80%. The stepper was set to stretch the sample to a level of 35% strain at the same rate (0.5 mm/s). Data collection was repeated five times under each dehydration condition. The compression resilience, RC% = S'/S*100%, and the hysteresis area were measured according to the stress-strain curves. The varying properties of the samples under different dehydration levels were investigated by fitting the curves. RESULTS: The area of the hysteresis loops observed in the stress-strain curves increased exponentially with dehydration levels, whereas the RC% decreased linearly. For all curves, low-strain stages can be explained by Hooke's law (σ = E0*ε). With increasing levels of dehydration, E0 was shown to increase, whereas the linear range was shortened. High-strain stages resembled exponential rather than the linear curves. And the nonlinear stage of the curve became increasingly apparent in the stress-strain curves of increased dehydration levels. CONCLUSIONS: The quantitative results in this study not only provide a numerical reference for future experimental measurements, but also can be used to verify the biphasic model in future studies.