Application of a new, self-recording, vibratory sensation meter to measure temporary threshold shift of vibratory sensation caused by local vibration exposure.

A new, self-recording, vibratory sensation meter measures temporary threshold shifts of vibratory sensation (TTSv) on a finger tip. After exposure to hand-transmitted vibration with exposure frequencies 63 Hz, 200 Hz and 500 Hz, and levels of acceleration 1 g, 2 g, 4 g and 8 g, fingertip measurements were obtained. Temporary threshold shift immediately after the vibratory exposure (TTSv,0) was estimated for each exposure from the regression analysis by approximation of an exponential function. Time constant (tc) was also estimated at the same time by the analysis. The coefficients of determination were large. Thus, the fit of the exponential function is very good for each exposure. The tc corresponds to the recovering velocity of the temporary shift and implies the half-life period of TTSv. These parameters enable us to examine more generally the relationships of TTSv to the characteristics of exposure vibration, subject and other conditions. On this basis, the estimated TTSv,0 and tc were used to examine the dependency of TTSv on the characteristics of the exposure vibration and the subject. The most effective frequency under the level of 4 g is thought to be between 200 Hz and 500 Hz. TTSv,0 of each subject proportionally increased with power of acceleration. The coefficient of determination on regression analysis was large. This result enables us to estimate TTSv,0 at an arbitrary level of acceleration by use of a regression equation derived from experimental data.