Quantification of the false vocal-folds effects on the intra-glottal pressures using large eddy simulation

During the closing phase of the phonation cycle the true vocal-folds (TVF) have a convergent-divergent shape. The negative pressures generated by the flow through the glottal passage are producing closing forces acting on the TVFs towards the center of the larynx. Intra-glottal pressures can affect both vocal-fold vibration and voice production, since they can accelerate the closing phase. This has a positive impact on the voice quality. Large Eddy Simulation approach is used to investigate the intra-glottal forces generated solely by the flow during the closing phase. The influence of the gap between the false vocal-folds (FVFs) and the location of FVFs with respect to the TVFs are analyzed. Based on anatomical measurements, four different gaps between the FVFs and two different distances between the true and false vocal-folds are investigated for the same trans-laryngeal pressure. The TVFs gap is kept constant. All cases exhibit a non-symmetric flow behavior in the mid-frontal plane. As compared with the baseline, significant negative pressures were found acting on the TVFs when the false glottal width is below a certain threshold value. The closing forces are increasing when the FVFs are located at larger distances further downstream from the TVFs.