EFFECTS OF MASKING OF FORE-AND-AFT VIBRATION ON TRACTOR RIDE COMFORT

Abstract

Masking of fore-and-aft vibration under two-axis vibration can impact the ride comfort of a tractor driver. The conventional evaluation of vibration levels by application of different parameters: root mean square acceleration (Aw), daily exposure A (8), signal-to-noise (S/N) ratios, and power spectral density (PSD) does not take into consideration masking effects. Laboratory measurements were conducted to enhance the tractor's ride comfort. Two-axis broadband random vibration excitation was used on the subjects during simulated driving conditions. The subjects had to adjust to equal levels of stimulus sensation. They were subjected to vibration from both fore-and-aft and vertical directions at the same time. Level of excitation (0.55 m/s2 r.m.s., 1.75 m/s2 r.m.s., and 2.25 m/s2 r.m.s.) and seat backrest position (position K inclined 14° with respect to the vertical axis and position S in vertical position without inclination) were varied. For r.m.s. Head acceleration, the Masking Threshold (MT) was established in fore-and-aft and vertical directions. Different regression models were utilized to determine the influential factors that affect the tractor's ride comfort.