Objective: The purpose of this presentation is to compare the acoustic and kinematic physiology of vibrato and essential vocal tremor

Methods/Design: A total of 20 adult participants 18 – 85 years of age were recruited with 10 being classified as healthy controls. Healthy controls were classically trained female vocalists with no less than 5 years as a trained singer without voicing or singing problems as per a VHI total score of 20 points or less. In addition, 10 females diagnosed with essential vocal tremor participated in this study who demonstrated bilateral hand tremor for 3 or more years in addition to demonstrating a clinically perceptible vocal tremor during sustained phonation. Simultaneous acoustic and nasoendoscopic recordings were acquired from all participants during production of sustained phonation of /a/ and /i/ at comfortable pitch and loudness for no less than 2 seconds duration. Acoustic recordings were obtained using an AKG head-mounted condenser microphone (model C520) and pre-amplifier (Symetrix 302 Dual Mic Pre-amp) using AD Instruments 8-channel PowerLab (Model PL 3516) and LabChart Pro (version 8.1) simultaneously with laryngeal imaging. Audio signals were recorded at 40 kHz sampling rate during sustained phonation. Laryngeal imaging was obtained using the Pentax Medical Nasolaryngoscope System.

Between group comparisons were conducted related to measurement of acoustic modulation rates and extent of fundamental frequency (f0) and sound pressure level (SPL). In addition, a comparison was made between upper airway structures observed to oscillation during production of vibrato versus vocal tremor.

Results: Outcomes showed that vocal tremor and vibrato involved similarly observed oscillation of upper airway structures involving the pharynx, base of tongue, vertical, horizontal, and lengthwise oscillation of the larynx across subjects. However, those with essential vocal tremor exhibited a slower acoustic rate and more variable extent of f0 and SPL modulation than found in those producing vibrato.

Conclusions: In addition to the uncontrollable production of modulation of the voice during sustained phonation in those with essential vocal tremor, affected individuals also showed a slower rate and more variable extent of acoustic modulation of f0 and SPL than those producing vibrato. The outcomes of this study highlighted similarities and differences between individuals producing vibrato compared to essential vocal tremor.