ObjectiveThe aim of this study was to investigate how the maximum area declination rate (MADR) of the glottis corresponds to the maximum velocity of the self-oscillating vocal folds just before their collision. The maximum velocity before collision is closely related to impact stress in the colliding vocal folds and, thus, it is an important indicator of vocal loading. MethodsHigh speed imaging data for a male subject and measurements of the glottal area waveforms performed on a physical 1:1 scaled model for phonation on vowel [u:] were compared with those obtained during a semi-occluded vocal tract which increases voice source-vocal tract interaction. Semi-occlusion was obtained by phonation through a glass resonance tube with the distal end in air or submerged 10 cm in water. ResultsThe results show that the area declination rate of the glottis, i.e., closing velocity, before the glottal closure is substantially lower than the MADR, and also lower in semi-occluded vocal tract phonation through a tube into air and into water than in vowel phonation. ConclusionsThe results suggest that MADR is not a reliable estimate of impact stress, and that impact stress in tube therapy is lower than in vowel phonation.