Effects of vocal loading on the phonation and collision threshold pressures

Phonation threshold pressures (PTP) have been commonly used for obtaining a quantitative measure of vocal fold motility. However, as these measures are quite low, it is typically difficult to obtain reliable data. As the amplitude of an electroglottograph (EGG) signal decreases substantially at the loss of vocal fold contact, it is mostly easy to determine the collision threshold pressure (CTP) from an EGG signal. In an earlier investigation (Enflo & Sundberg, forthcoming) we measured CTP and compared it with PTP in singer subjects. Results showed that in these subjects CTP was on average about 4 cm H2O higher than PTP. The PTP has been found to increase during vocal fatigue. In the present study we compare PTP and CTP before and after vocal loading in singer and non-singer voices, applying a loading procedure previously used by co-author FP. Seven subjects repeated the vowel sequence /a,e,i,o,u/ at an SPL of at least 80 dB @ 0.3 m for 20 min. Before and after the loading the subjects’ voices were recorded while they produced a diminuendo repeating the syllable /pa/. Oral pressure during the /p/ occlusion was used as a measure of subglottal pressure. Both CTP and PTP increased significantly after the vocal loading.