Glottic behavior in vocal fry. A preliminary study using LVS & HSDP with analysis by kymography, P-FFT & Nyquist plots
Glottal fry voice falls within the lowest range of the human vocalization and is produced voluntarily or as a part of dysphonia. Although acoustics of fry are common, physiologic data are scarce, specifically with regard to glottis behavior. LVS and nowadays HSDP provide a whole new way to visually investigate laryngeal behavior and glottis posturing during any phonatory modes, providing detailed real-time information about laryngeal biomechanics (e.g., mucosal wave, wave motion directionality, glottic area wave form, asymmetry of vibrations within and across vocal folds (VF), and contact area of the glottis. These observations are fundamental to our understanding and modeling of both normal and disordered phonation. In this preliminary report, we focus on direct HSDP in vivo observations of not only the glottic region, but also on the entire supraglottic laryngeal posturing during production of vocal fry. In subsequent reports we examine hiss and over-pressured phonation modes produced in a non-pathological setting. We also contrast these findings to normative phonation and to each other. Analysis includes spatio-temporal vibration patterns of VF, multi-line kymograms, spectral P-FFT analysis, and Nyquist spatio-temporal plots. The presented examples reveal that supraglottic contraction assists in prolonged closed phase of the vibratory cycle and that the prolonged closed phase is long in vocal fry. These findings need to be compared to pathologic phonation containing vocal fry voice in order to arrive at a better differential diagnosis and if/when a better treatment protocol is desired.