Human reactions to whole-body transverse angular vibrations compared to linear vertical vibrations.

An electro hydraulic vibration device was used to study the effects of some forms of angular motion in the transverse mode and a combination of angular transverse and vertical motion, common in ground vehicles. Heart rate, tracking error, hip and shoulder acceleration, and subjective judgements of three subjects were recorded under different test conditions using three different seats. The excitation acceleration had a 0-25 and 0-50 g peak to peak linear component on the seat at frequencies of 1, 1-7, 2-5, and 40 Hz. Man is more affected and shows more degraded performance under the influence of transverse angular vibration than under vertical vibrations alone. Worst is a combination of transverse angular and vertical motion. Tractor seats good for vertical vibrations are not necessarily good for transverse vibrations