Effects of simulated source of tremor on acoustic and airflow voice measures

To test the effects of different sources of tremor on the voice, tremor was simulated by external rhythmic perturbation of structures at the subglotta l, glottal, and supraglottal levels in 10 healthy subjects. The acoustic an d airflow signals simultaneously recorded during sustained phonation in the normal and the 3 simulated tremor conditions were analyzed and compared. V oice measures included: fundamental frequency, 2 short-term perturbation me asures (jitter and shimmer), and 3 long-term tremor measures (prominence ra tios of the spectral peaks of the acoustic frequency contour, acoustic ampl itude contour, and airflow contour). Measures of fundamental frequency and percent shimmer were not significantly affected by the simulated tremors. M easures of percent jitter and the amplitudes of the long-term frequency and amplitude modulations were most prominently increased when respiratory dri ve was perturbed by simulated tremor. Spectral analysis of the acoustic amp litude contour was most useful in distinguishing the 3 sites of simulated t remor.