Threshold Pressure For Vocal Fold Collision

Phonation threshold pressure (PTP) is frequently used for characterizing vocal fold vibration properties. However, because of the very low pressures, it is often difficult to measure PTP with acceptable accuracy. This investigation analyses an alternative pressure, the collision threshold pressure (CTP), defined as the lowest pressure required to initiate vocal fold collision. Fourteen amateur singers – six female and eight male – served as subjects. They were recorded while repeating the syllable /pa:/ with a gradually decreasing degree of vocal loudness. Several pitches were recorded before and after vocal warm-up by means of an audio microphone, an electroglottograph (EGG) and a pressure transducer, which the subjects held in the corner of their mouths and which hence reflected oral pressure. The amplitude of an EGG signal increases substantially when the vocal folds make contact, i.e., collide, thus allowing simple measurement of the CTP. The oral pressure during the p-occlusion was used as for estimating subglottal pressure. CTP and PTP tended to be higher before than after the warm-up, although the differences varied greatly both between given subject’s pitches and between subjects. Repeated measurements on two subjects showed lower standard deviations for CTP than for PTP. The results support the conclusion that CTP is a promising parameter in investigations of vocal fold characteristics.