Correlates of temporal high-resolution formant analysis and glottal excitation in laryngeal dystonia before and after botulinum toxin treatment: a case study

This study visualizes the glottal excitation in a temporally highly resolved estimate of the first formant. Instantaneous estimates during the glottal cycle of the frequency and bandwidth of the first formant closely follow the electroglottographic contour. This is demonstrated for phonation of an [a:] produced by one female patient with laryngeal dystonia. The observed contours in the F1 frequency and bandwidth can be interpreted with reference to the current status of patients' typical phonation behaviour before and after botulinum toxin (BTX) treatment. The temporally highly resolved formant frequency and bandwidth contours reflect glottal features such as the different durations of the open phase and fundamental frequency and/or amplitude perturbations of the vocal fold vibration. For example, diplophonia is identifiable in parts of the phonation. These results suggest the possibility of quantifying differences in the intra-cycle first formant contours according to different voice qualities.