The apparent mass of the seated human exposed to single-axis and multi-axis whole-body vibration

Apparent Mass and Seat-to-head Transmissibility Responses of Seated Occupants under Single and Dual Axis Horizontal Vibration

“…It has been shown that the proposed W d -weighting correlates reasonably well with the biodynamic responses of the body seated without a back support 4) . The biodynamic responses of the occupants seated with a back support and exposed to fore-aft WBV, however, differed significantly from those corresponding to sitting with a back support and exposed to lateral vibration 1,3,4,6,8) . The characterisation of biodynamic responses of the body seated assuming typical driving postures (back and hands supports) is thus essential for defining adequate frequency weightings for exposure assessments.…”

“…The biodynamic responses of the seated occupants exposed to whole body vibration (WBV) have been widely investigated in terms of apparent mass (APMS) or driving-point mechanical impedance, seat-to-head vibration transmissibility (STHT) and absorbed power, under broad ranges of vibration and postural conditions [1][2][3][4][5][6] . The majority of these studies focus on response analyses of seated body exposed to vertical vibration although a few have investigated the responses to foreaft (x) and lateral (y) vibration 1,3) .…”

“…Furthermore, most of the studies have been limited to single-axis vibration and response measurements in the direction of the applied vibration. Only a few recent studies have measured the seated occupants apparent mass responses to orthogonal dual and three-axis vibration [5][6][7] and only a single study has obtained cross axis responses of seated occupants exposed to dual-axis vibration 7) . Studies on horizontal biodynamics have mostly considered a sitting posture without a back support with only few exceptions [6][7][8] .…”

“…Only a few recent studies have measured the seated occupants apparent mass responses to orthogonal dual and three-axis vibration [5][6][7] and only a single study has obtained cross axis responses of seated occupants exposed to dual-axis vibration 7) . Studies on horizontal biodynamics have mostly considered a sitting posture without a back support with only few exceptions [6][7][8] . The vast majority of the studies reporting the biodynamic responses of subjects seated with back support have primarily focused on the body interactions with the seatpan alone, although the backrest is known to serve as an important secondary driving-point 3,9) .…”

“…Recent studies on seated occupants biodynamic to dual and three-orthogonal axis vibration have consistently reported similar seatpan APMS response trends, but slightly lower resonant frequencies and magnitudes compared to the single axis APMS responses [5][6][7] . These studies have considered either back supported or hands supported postures, although not both, and did not attempt measurements at the backrest and vibration transmitted to the head.…”