Imaging of auto-oscillating vocal folds replicas with left–right level difference due to angular asymmetry

Abstract

Vertical level difference due to vertical angular asymmetry (up to 20 • ) between the normal (right) and tilted (left) vocal fold (VF) is experimentally assessed in the framework of unilateral vocal fold paralysis. The upstream pressure and high-speed vibration imaging for different camera view angles are assessed during steady-state auto-oscillation of three different mechanical VF replicas. A global image-based correlation allows to assess the oscillation frequency independently from the camera view angle. Resulting oscillation frequencies matches the ones obtained from aerodynamic data. Mean vibration cycles obtained from videokymographic line-scans at different positions along the posterior-anterior direction are analysed. Left-right VF displacement phase difference, axis shift and left-right mucosal wave phase difference are identified as essential parameters quantifying angular asymmetry. The influence of the degree of angular asymmetry, scan position and replica is discussed.

Dynamic vibration mode decomposition of auto-oscillating vocal fold replicas without and with vertical tilting

“…1(c). The setup is similar to the one described in [12,13]. Airflow, characterised by volume flow rate Q (sampling frequency 0.5 kHz), is applied along the inferior-superior direction as depicted in Fig.…”

“…The overall vertical level difference h in absence of airflow is obtained from the experimentally imposed α following a geometrical reasoning as outlined in [13] (section 2.3 therein) and yields half of the maximum vertical level difference along the triangular air leakage area indicated in Fig. 1(c).…”

“…The molded VF replicas are briefly detailed in Section 2. In previous studies [12,13], these three replicas were used to study the effect of vertical tilting of a single VF on their autooscillation. Concretely, the right VF was kept in place whereas the posterior edge of the left VF was tilted in the medio-sagittal plane towards the superior direction as shown in Fig.…”

“…In [12], the upstream pressure driving VF auto-oscillation was analysed for Local VK line-scan analysis [13] showed the influence of angular asymmetry on VF vibration. In this work, it is sought to further investigate sustained steady state VF vibration without (α = 0 • ) and with (α > 0 • ) angular asymmetry by analysing high-speed (HS) image sequences of the vibrating VF's.…”

“…Instead of focusing on local spatial features or line scans [13,15,17,18] it is sought to assess simultaneously temporal as well as spatial information of the global VF's auto-oscillation. A dynamic vibration mode decomposition (DMD) of the observed vibration snapshots is applied as other VF vibration mode decomposition methods such as the empirical eigenfunction analysis [19] do not inform on the temporal mode dynamics.…”