Laryngeal function associated with changes in lung volume during voice and speech production in normal speaking women

The present study explored possible relations between respiratory and laryngeal function associated with changes in lung volume level during phonation. Respiratory, acoustic, aerodynamic, electroglottographic, and videostroboscopic measures were obtained simultaneously for 14 normal female speakers as they sustained vowels and syllable repetitions throughout the vital capacity. Statistical analyses compared group performances between (a) high and mid lung volumes; and (b) mid and low lung volume levels. Significant differences were found for (1) vertical laryngeal position (VLP); (2) amplitude of vocal fold vibration; (3) minimum flow; (4) degree of glottal closure, and (5) degree of laryngeal compression. Results indicated that during phonation at high lung volumes the larynx displays an overall "more dilated" configuration with a lower position in the neck, larger amplitudes of vocal fold vibration and larger posterior glottal gaps during the closed phase of vocal fold vibration. Conversely, during phonation at low lung volumes the larynx seems to adopt a more constricted configuration, with a more elevated position, smaller amplitudes of vocal fold vibration, more complete glottal closure during the closed phase of vocal fold vibration, and increased degree of compression. Results also indicated that while some vocal function measures displayed different absolute values for sustained vowels as compared to syllable repetitions, the patterns of change were similar for both speech tasks. Individual subject data reflected alternative patterns of laryngeal behavior for achieving the speech tasks. The results were interpreted as evidence that laryngeal function during voice production is clearly influenced by the lung volume at which phonation is produced. Possible underlying physiological mechanisms are discussed. These findings contribute to better understanding of the normal vocal mechanism when phonation is produced outside of the normal mid-range of lung volumes typically used in conversational speech