The Influence of Pitch and Loudness Changes on the Acoustics of Vocal Tremor

dromey{at}byu.edu

The effect of tremor on phonation is to modulate an otherwise steady sound source in its amplitude, fundamental frequency, or both. The severity of untreated vocal tremor has been reported to change under certain conditions that may be related to muscle tension. In order to better understand the phenomenon of vocal tremor, its acoustic properties were examined as individuals volitionally altered their pitch and loudness. These voice conditions were anticipated to alter the tension of the intrinsic laryngeal muscles. The voices of 10 individuals with a diagnosis of vocal tremor were recorded before participating in a longitudinal treatment study. They produced vowels at low and high pitch and loudness levels as well as in a comfortable voice condition. Acoustic analyses quantified the amplitude and frequency modulations of the speakers' voices across the various conditions. Individual speakers varied in the way the pitch and loudness changes affected their tremor, but the following statistically significant effects for the speakers as a group were observed: Higher pitch phonation was associated with a more rapid rate for both amplitude and frequency modulations. Amplitude modulation became faster for louder phonation. Low-pitched phonation led to decreases in the extent of amplitude tremor. Varying pitch led to dramatic changes in the phase relationship between amplitude and frequency modulation in some of the speakers, whereas this effect was not apparent in other speakers.

KEY WORDS: tremor, acoustics, voice disorders, neurology

Submitted on November 6, 2001
Accepted on June 17, 2002

This article has been cited by other articles:

				K. A. Farinella, T. J. Hixon, J. D. Hoit, B. H. Story, and P. A. Jones Listener perception of respiratory-induced voice tremor. Am J Speech Lang Pathol, February 1, 2006; 15(1): 72 - 84. [Abstract] [Full Text] [PDF]