A study was designed to determine the rate of growth of discomfort, the absolute level of discomfort, and the principal locations of discomfort arising from exposure to roll, lateral, pitch and fore-and-aft oscillation of subjects seated on a flat rigid seat and on a rigid seat with a backrest. The study also tested whether exposure to rotational and translational stimuli in the same plane, with matched accelerations in the plane of the seat, results in similar rates of growth of discomfort and similar absolute discomfort.
The results showed that the presence of a backrest reduced the discomfort experienced by subjects at frequencies between 0.25 and 0.4 Hz. The results showed that the discomfort arising from rotational and translational motions has a broadly similar character below 0.5 Hz, while above 0.5 Hz subjects were more sensitive to rotational than to translational oscillation.