Vibration and comfort IV. Application of experimental results

In this conclusion to a four-part series of papers, an interpretation of the experimental data presented in the earlier three papers is given. The results obtained from the experiments are compared with those obtained by other researchers. A set of simplified approximations to the various equivalent comfort contours are defined and a general approach to the prediction of discomfort due to multi-axis, multi-input complex vibration is given. It is shown that the results for translational vibration of a seat surface supporting the body are reasonably consistent with some previous studies. Although the contours for fore-and-aft and lateral vibration are in agreement with those in ISO 2631 (1978) there is evidence that sensitivity to vertical seat vibration above 8 Hz should be greater than defined in that standard. It is shown that the results for rotational seat vibration differ by an order of magnitude from those published by other authors but that this difference may be explained by the positions of the centres of rotation used in other studies. It is shown that simple approximations to the median equivalent comfort contours for translational and rotational seat vibration and translational foot and back vibration may be defined by contours on acceleration frequency graph having a slope of 0 dB per octave (constant acceleration) and 6 dB per octave (constant velocity). For most conditions these contours fall within the 25th-75th percentile of the experimental data. The application of these contours as frequency weightings for general vibration evaluations is discussed.</p