Motion sickness: Effect of the frequency of lateral oscillation

Introduction: Low-frequency lateral oscillation is a cause of motion sickness in some forms of transport. However, the relationship between occurrence of sickness and the frequency of lateral oscillation is not known. This paper presents a study of motion sickness with lateral oscillation at frequencies between 0.0315 Hz and 0.20 Hz. Method: There were 120 subjects, in 6 groups of 20, who were exposed for up to 30 min to sinusoidal lateral oscillation with a peak velocity of 1.0 ms(-1) at one of six frequencies (0.0315, 0.05, 0.08, 0.125, 0.16, 0.20 Hz). Subjects provided ratings of their motion sickness symptoms at 1-min intervals. Results: There was a highly significant effect of the frequency of lateral oscillation on the occurrence of mild nausea. Discussion: The present results have been combined with those from a previous experiment conducted with higher frequencies of oscillation to produce a frequency weighting for motion sickness caused by lateral oscillation over the range 0.0315 to 0.8 Hz. Conclusions: Mild nausea caused by lateral oscillation may be predicted by an acceleration frequency weighting that is independent of frequency from 0.0315 to 0.25 Hz and reduces at 12 dB per octave (i.e., proportional to displacement) from 0.25 to 0.8 Hz. This weighting differs from the frequency weighting currently used for predicting motion sickness caused by vertical oscillation. The frequency weighting for lateral oscillation may not be applicable in those environments in which there is roll motion during lateral oscillation.