ABSORPTION OF ENERGY DURING WHOLE-BODY VIBRATION EXPOSURE

Absorbed power, P-Abs, during exposure to vertical and horizontal whol e-body vibration in sitting posture was measured using 15 male and 15 female subjects. Different experimental conditions were applied, such as vibration level (0.25-1.4 m/s(2)), frequency (1.13-80 Hz), body wei ght (54-93 kg), relaxed and erect upper body posture, Results show tha t P-Abs was strongly related to frequency of the vibration peaking, wi thin the range of 4-6 Hz and below 2.5 Hz for vertical and horizontal directions respectively. P-Abs increased with acceleration level and b ody weight. If risk assessment is based on the assumption that the amo unt of P-Abs independence of the frequency of the vibration, indicates a hazard, then the frequency weighting procedure in ISO-standard 2631 can be questioned. The ISO weighting for horizontal vibration seems t o underestimate the risk for frequencies within the range of about 1.5 -3 Hz and overestimate them above about 5 Hz. For the vertical directi on the frequency weighting overestimates the risk for frequencies abov e about 6 Hz. The results also indicate a need for differential guidel ines for females and males. Many types of vehicle produce whole-body v ibration with frequencies in the range where the highest P-Abs was obs erved. Although not yet thoroughly evaluated, P-Abs may be a better qu antity for risk assessment than acceleration as specified in ISO 2631, since it also takes into account the dynamic force applied to the hum an body. (C) 1998 Academic Press.