The Vibration Discomfort of Standing Persons: The Effect of Body Supports

Abstract

When standing and exposed to vibration in trains, passengers and crew may seek support by leaning on a surface or holding a bar or a handle that alters the transmission of vibration to their bodies. The effects of such contact on the discomfort caused by vibration have not been previously investigated. This study was designed to investigate the effects of postural supports on the discomfort caused by fore-and-aft and lateral whole-body vibration in the frequency range 0.5—16 Hz. Using the method of magnitude estimation, 12 standing male subjects judged the discomfort caused by five magnitudes of sinusoidal vibration at six frequencies (0.5, 1.0, 2.0, 4.0, 8.0, and 16 Hz) and in two directions (fore-and-aft or lateral) while using four different postural supports: no support, holding a vertical bar, leaning with back support, and leaning with shoulder support. Equivalent comfort contours were constructed, showing how discomfort depends on the vibration frequency over a range of vibration magnitudes with each support. Compared to standing with no support, holding a vertical bar had only a minor effect on the discomfort caused by either fore-and-aft or lateral vibration. At frequencies greater than about 2 Hz, leaning backwards against a back support increased the discomfort caused by fore-and-aft vibration and leaning sideways against a shoulder support increased discomfort caused by lateral vibration. Frequency weightings derived from the equivalent comfort contours show that the weightings suggested in current standards do not provide good predictions of the frequency dependence of discomfort caused by vibration when standing without any support or when supported and holding only a bar. It is concluded that leaning, with the back or shoulder supported, increases the discomfort caused by vibration in a direction normal to the body surface at frequencies greater than about 2 Hz. Currently, standardized frequency weightings do not provide good predictions of the discomfort caused by horizontal vibration when standing without holding a support.

Keywords

vibration discomfort standing supports

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