Methods of quantifying vibration with respect to human response are fully defined. The procedures may be applied to all types of vibration: multiple-axis and multiple-input motions which are steady-state, random or transient. The procedures are based on experimental research and have been applied to predict the discomfort, annoyance, health risks, interference with activities and motion sickness associated with vibration measured in a wide range of environments.
The general method involves the assessment of 12 axes of vibration (the 3 translational and 3 rotational axes on a seat surface, the 3 translational axes at the seat back and the 3 translational axes at the feet). The method may be simplified so as to include only those axes of interest in specific environments.
A scale of approximate discomfort, an ‘action level’ guide to the prevention of health effects, magnitudes of vibration which may interfere with activities, and a means of predicting the probability of motion sickness are provided. In all cases the frequencies, axes, locations and durations of the motions responsible for adverse effects can be identified. The application of the procedures to evaluate measurements in vehicles, assess computer predictions of vehicle vibration and optimise seat dynamics is described.