Collision and phonation threshold pressures before and after loud, prolonged vocalization in trained and untrained voices

The phonation threshold pressure (PTP) is defined as the lowest subglottal pressure needed for obtaining and sustaining vocal fold oscillation. It has been found to increase during vocal fatigue. In the present study, PTP is measured together with the threshold pressure needed for vocal fold collision; henceforth, the collision threshold pressure (CTP). PTP and CTP are compared before and after loud, prolonged vocalization in singer and nonsinger voices. Ten subjects repeated the vowel sequence /a, e, i, o, u/ at a Sound Pressure Level of at least 80 dB at 0.3 m for 20 minutes. Audio and electroglottography signals were recorded before and after this exercise. At the same time, oral pressure was registered while the subjects produced a diminuendo repeating the syllable /pa:/, thus acquiring an approximate of the subglottal pressure. CTP and PTP increased significantly after the vocal loading in the nonsinger subjects. On the other hand, singers reported no substantial effect of the exercise, and most singers had a mean after-to-before ratio close to 1 for both CTP and PTP.