Glissando: laryngeal motorics and acoustics.

The objective of this study was to investigate the laryngeal mechanisms and the acoustical signal during a glissando. In particular, glottal length, maximum glottal area, and vibratory amplitudes during a glissando maneuver of a healthy male adult were measured. An endoscopic high-speed system combined with a laser projection device was used to obtain quantitative data both in the time and spatial domains. Simultaneously to the endoscopic investigation, the acoustic signal was recorded. Fundamental frequency and sound pressure level derived from the acoustic recordings were compared to vocal fold length and glottis area derived from the high-speed recordings. Results were used for interpretation of the phonation mechanism during glissando by means of laryngeal and acoustic parameters. The transition between the chest register and the falsetto register was identified by the absence of vocal fold contact. A rather early onset of the falsetto register was observed at 160 Hz. Although fundamental frequency of the vocal folds increased linearly even at the transition point, sound pressure level dropped down. These data represent the first ever quantitative description and interpretation of the glissando based on both voice properties and laryngeal motorics. In the presented example of an untrained singer, the falsetto sets in at comparatively low frequencies. Although the chest-falsetto transition is rather smooth for laryngeal motorics and voice pitch, a sudden drop of voice intensity was observed.