COMFORT CONTOURS: INTER-AXIS EQUIVALENCE

Abstract Inter-axis equivalence for sinusoidal vibrations as stipulated by ISO/DIS 2631 for seated persons was studied by adjusting the acceleration of a horizontal sinusoidal test vibration ( x ∨ y ) until it caused equal sensation as a vertical sinusoidal reference motion of the same frequency. The reference vibrations consisted of sine waves ranging from 1·6 to 12·5 Hz and were presented with three weighted accelerations of a zw =0·3, 0·6 and 1·2 ms −2  r.m.s. (reference contours). 26 subjects (15 men, 11 women, 20–55 yrs, 153–187 cm) participated in the respective experiments. Based on the three reference contours, predicted values for horizontal motions were calculated by using the weighting factors provided in ISO/DIS 2631. The International standard was confirmed insofar as the shape of the contours determined for horizontal motions was independent from vibration magnitudes as sensitivity to fore-and-aft and to lateral motions was similar. However, the accelerations adjusted for horizontal vibrations were considerably lower than predicted, suggesting that the weighing factors provided in ISO/DIS 2631 need to be corrected.