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The Transmission of Vertical Vibration to the Heads and Shoulders of Seated Men.

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Modern forms of transportation can impose high levels of vibration upon occupants. To determine the effects of vibration, it is necessary to define the vibration levels experienced by such people as passengers, drivers or pilots. This definition should preferably quantify not only the input levels but also those at the parts of the body most likely to be affected by the vibration. This report covers an investigation of the frequency response of the human body to vertical vibration, using six subjects on a rigid seat. The input used was a swept sine acceleration, where the frequency of vibration varied linearly with time between an upper and lower value, at a fixed amplitude. Use of such an input facilitated measurements of amplitude ratio and phase angle plots of the ratio of head and shoulder acceleration to seat acceleration against frequency, to be made for various postures and limb positions. Both resting the back against the seat and putting the legs forward had a major effect on transmission. Attempts were made to model these response curves so that by simply monitoring floor vibration in vehicles and assuming the seat response is known, one can predict the range of vibrations present at the head and shoulders. Theoretical analysis was used to demonstrate that the response of cushions is directly related to the human frequency response.

Subject Categories:

  • Stress Physiology
  • Human Factors Engineering and Man Machine Systems

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