Abstract
To explore the voice regulating system during sustained phonation kept at a comfortable level, air flow, intensity and frequency level were examined under a variety of conditions. Experiments consisted of four conditions : 1) normal condition 2) keeping constant flow 3) keeping constant intensity 4) exposure to 125Hz band noise. In the second and the third experiments, test subjects wereinstructed to keep their constant level of air flow or intensity for five seconds, while watching loci on a CRT and in the fourth experiment, 70dB band noise was given one second after test subjects produced voice.
Results : Air flow decrease over the time course was observed in all of the tests. Intensity showed a slightly decreasing level over the time course, and frequency was maintained at a constant level during the tests in each subjects.
Decrease of air flow implies the improvement of air flow consumption efficiency in sustained phonation, resulting from increasing resistance of the glottis. Decrease of intensity remains in a small range imperceptible to test subjects, which suggests that regulating system works on maintaining the voice intensity level during sustained phonation.
