Purpose The purpose of this study was to investigate the relation of respiratory forced oscillation to the acoustic characteristics of vocal tremor.

Method Acoustical analyses were performed to determine the characteristics of the intensity and fundamental frequency (F₀) for speech samples obtained by Farinella, Hixon, Hoit, Story, and Jones (2006)  using a respiratory forced oscillation paradigm with 5 healthy adult males to simulate vocal tremor involving respiratory pressure modulation. The analyzed conditions were sustained productions of /a/ with amplitudes of applied pressure of 0, 1, 2, and 4 cmH₂O and a rate of 5 Hz.

Results Forced oscillation of the respiratory system produced modulation of the intensity and F₀ for all participants. Variability was observed between participants and conditions in the change in intensity and F₀ per unit of pressure change, as well as in the mean intensity and F₀. However, the extent of modulation of intensity and F₀ generally increased as the applied pressure increased, as would be expected.

Conclusion These findings suggest that individuals develop idiosyncratic adaptations to pressure modulations, which are important to understanding aspects of variability in vocal tremor, and highlight the need to assess all components of the speech mechanism that may be directly or indirectly affected by tremor.