Abstract
It is necessary to clarify the vibration characteristics of a seated human body for the interpretation of the influence on the seated human body exposure to whole-body vibration. The results of a lot of past studies have informed that the difference of seated postures changes vibration characteristics such as the resonance frequency and the resonance amplitude of a seat-to-head transmissibility and a driving-point apparent mass. However, the seated postures of their subjects in these studies are not necessarily explained in detail. Though the evaluation of human exposure to whole-body vibration are specified by ISO2631, the seated postures at the experiments aren't specified in any ISO standard. In order to make good use of the results of the human vibration experiments, a technical report about the seated postures at the experiments are being discussed. Therefore the purpose of this paper is the expression of the seated postures at the experiments by the index values for seated posture defined by the technical report and the mention of the relation between the seated posture and resonance frequencies of the transmissibility and the apparent mass. The vibration of the experiment was the vertical random vibration whose frequency is from 2 to 30 Hz. The experiments of two different seated postures, an upright posture and a relaxed posture, were performed. In the result, these resonance frequencies in the relaxed posture were lower than those in the upright posture. It is suggested that the lumbar curvature has a relationship with these resonance frequencies.
