Perception thresholds for vertical vibration at the hand, seat and foot

In many occupational and leisure environments, the human body is exposed to oscillatory motions of handles, seats and floors which give rise to complex patterns of sensations. Knowledge of differences in sensitivity to the perception of vibration at the hand, seat and foot would assist the identification of sources of discomfort caused by vibration. The objective of this study was to examine the effect of vibration frequency (8 to 315 Hz for the hand and foot, 2 to 315 Hz for the seat) and input location (the hand, seat and foot) on thresholds for perception of vertical vibration. Perception thresholds were determined with 36 males aged 20 to 30 years divided into three groups of 12 subjects; each group received vertical vibration at either the hand, or the seat, or the foot. At frequencies less than 50 Hz, sensitivity to vertical vibration at the seat was the greatest and sensitivity to vertical vibration at the hand was least (p<0.04). The differences in median sensitivity between the three locations were greatest at low frequencies: at 50 Hz the ratios of perception thresholds (ms r.m.s) for the three inputs were about 1.0 (seat):1.5 (foot):3.0 (hand); at 10 Hz the ratios were 1.0 (seat):3.0 (foot):5.0 (hand). A similarity in the shapes of the threshold contours at frequencies greater than 80 Hz suggests the same psychophysical channel mediated high frequency thresholds at the hand, seat and foot.