Control Mechanism of Vocal Intensity in Normal Subjects

We studied the regulatory mechanism for vocal intensity by aerodynamic phonatory examination, including direct extraction of subglottic pressure through the glottis. PS-77 phonatory test equipment and the PI-100 phonatory analyzing system were applied to measure air flow rate, pitch and intensity of voice, subglottic pressure, glottal resistance, subglottal power and laryngeal efficiency. 9 normal subjects (4 males and 5 females) were tested in the following ways: 1) easy phonation for several seconds; 2) phonation from weak to louder (crescendo) continuously within one breath, keeping the same pitch level in the chest and falsetto registers. Results: In the easy phonation, the values of subglottic pressure, glottal resistance, laryngeal efficiency showed no difference between males and females, but the values of subglottic power in men were larger than those in females. In the crescendo in the chest register, values of subglottic pressure, glottal resistance, glottal power and laryngeal efficiency increased linearly, but the air flow rate did not change intensity increased. In the falsetto register, high values were observed for air flow rate, subglottic pressure, glottal resistance and glottic power, while a low value of laryngeal efficiency was observed to the chest register at the same intensity level. These parameters all increased in parallel with increasing intensities, with close correlations.