High-speed video analysis of the phonation onset, with an application to the diagnosis of functional dysphonias.

An objective method for the diagnosis of functional dysphonias is presented. The mathematically motivated approach was evaluated on 71 female subjects with normal voice or functional dysphonia. Using digital high-speed recordings, the phonation onset process was recorded in real-time for 8-10 different sound pressure levels for each subject. From these recordings two parameters were mathematically estimated, reflecting the phonation onset dynamics. The growth of the vocal fold amplitudes during the phonation onset process was described by a parameter a for which its lower threshold value a(th) was extrapolated. This threshold reflects the myoelastic tonus within the vocal folds. The second parameter was the maximum sound pressure level L(max). It allows conclusions on voice efficiency with respect to the necessary subglottal pressure and the myoelastic forces. Due to the significant differences of these parameters between the pathological groups and normal voices, the presented method is a stable and objective tool for medical diagnosis.