Comparative measures of vocal tremor and vocal vibrato

Acoustic analyses were carried out on vocal vibrato produced by nine opera singers and vocal tremor accompanying the sustained phonation of patients with the following diagnoses: Parkinson's disease, amyotrophic lateral sclerosis, spinal muscular atrophy, essential tremor, and adductor spastic dysphonia. While vocal tremor on average had a faster oscillatory rate and greater amplitude extent when compared to vocal vibrato, only the cycle to cycle measures of shimmer and jitter differed significantly between these groups. However, these differences existed even when the effect of the oscillation was removed. These data are consistent with the hypothesis that vocal vibrato in singers and vocal tremor in patients may be part of the same continuum.