Sinusoidal and random whole-body vibration: comparative effects on visual performance.

An experimental comparison of the effect of whole-body sinusoidal and one-third octave-band random vibration on the performance of a display reading task is described. The findings indicate that one-third octave-band random vibration has significantly less effect on performance. Subsequent measurements of rotational head motion demonstrated that this finding may be due to differences in the velocity probability density distributions produced by the different motions. Subjects also performed the visual task during exposure to several broad-band random motions. Predicted error values were obtained by averaging the frequency weighted time histories of these motions. It was found that both R.M.S. and R.M.Q. averaging procedures applied to the broad-band frequency weighted time histories gave accurate error predictions when compared with the measured error scores. Practical implications of the experimental findings and recommendations for future research are discussed.