The significance of lateral whole-body vibrations related to separately and simultaneously applied vertical motions. A validation study of ISO 2631

Sensitivity of lateral motions relative to vertical motions were determined and compared to predictions provided by ISO 2631. Two experiments were exe cuted where lateral and vertical motions were applied consecutively or simu ltaneously and where the magnitude of a single- or dual-axis test signal wa s adjusted until it was judged as equivalent to a preceding single-axis ref erence motion of the same frequency. Experiment 1: References consisted of vertical sinusoidal motions presented with 1.6-12.5 Hz and weighted accelerations of a(zw) = 0.3, 0.6 and 1.2 m s(-2) r.m.s., single-axis test signals were lateral motions of the same fre quency. 26 subjects (15 men, 11 women, 20-56 yr) participated in the experi ments. Accelerations adjusted for lateral vibrations above 1.6 Hz were cons iderably lower than predicted suggesting that the weighting factors provide d in ISO 2631 are incorrect. Experiment 2: References consisted of single-axis vertical or lateral sinus oidal motions presented with 1.6-12.5 Hz and a weighted acceleration of a(z w) = 1.25 m s(-2) r.m.s. The dual-axis test signals consisted of a constant fraction of the reference acceleration (10, 25, 50, 75, 90%) and a perpend icularly oriented adjustable component. 31 subjects (15 men, 16 women, 19-5 1 yr) participated in the experiments. Both experiments revealed that ISO 2631 is qualitatively valid, the weighti ng of lateral motions above 1.6 Hz, however, should be increased in order t o meet the actual sensitivity particularly in case of multi-axis vibrations . (C) 1999 Elsevier Science Ltd. All rights reserved.