Glottic activity in vocal hiss. A preliminary study using LVS & HSDP with analysis by kymography, P-FFT & Nyquist plots
Hissy voice can be interpreted as the sound similar to a sound of a sibilant, either voiced and un-voiced (s/z). This voice quality can be present in pathological phonation or when it is used in normal phonation it is employed to convey emotional expressions to signal disapproval, annoyance, or even contempt. Vocal hiss or hissy voice is not well studied, specifically via physiologic examination of the glottis. In this preliminary study we used HSDP to examine the nature of the vocal hiss at the glottic and supraglottic levels. We decided on HSDP, because this technology provides a whole new way to visually investigate laryngeal behavior and posturing during phonation. It provides detailed real-time information about laryngeal biomechanics that include observations about: mucosal wave, wave motion directionality, glottic area wave form, asymmetry of vibrations within and across vocal folds (VF), and contact area of the glottis including posterior commissure closure. These observations are fundamental to our understanding and modeling of both normal and disordered phonation. In previous reports, we examined vocal fry using HSDP in vivo observations of not only the glottic region, but also on the entire supraglottic laryngeal posturing. Here we contrast hiss phonation mode produced in a nonpathological settings to normative phonation produced by the same speaker. As with fry, analysis included spatio-temporal vibration patterns of VF, multi-line kymograms, spectral PFFT analysis, and Nyquist plots. The presented examples reveal that supraglottic contraction is present in hiss but that it is short in duration. We speculate, that this contractual force allows for VF vibration despite glottic separation. These findings need to be compared to pathological phonation representing the three voice modes to derive a better differential diagnosis.