正弦振動の評価法 : 振動の評価法1

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Problems of measurement and evaluation of hand vibration as well as of the whole body vibration have recently been raised in the field of public unisance and industrial health. Many researchers have published various kinds of papers concerning the problems, however it is somewhat hard to derive clear evaluation methods from their results (Figs, 1, 2 and 3), because of difficulty of systematization. Psychological experiments were carried out by using new vibration tables of electro-dynamic type in vertical and horizontal directions, to establish a new systematic method of evaluation. Threshold level defined as the minimum perceptible vibration acceleration level and equal sensation level defined as the vibration level of the other frequency of the same vibration sensation as that at 20 Hz were observed by the method of paired comparisons on the whole body in sitting, standing and lying postures and on the hand (Fig. 6, 8 and 9). It is shown in Fig. 6 that there is no difference in the threshold curves (T curves) between sitting and standing postures, and that the T curve of the horizontal vibration is higher by 10 dB than that of the vertical vibration in the domain above 5 Hz. Characteristic feature of the T curve of the lying posture in Fig. 8 is its dip near 80 Hz for the vertical vibration due to skull resonance. In Fig. 9, the T curves of hand for both vibrations are in sufficient agreement. No clear differences in the equal sensation curves (ES curves) between sitting and standing postures were observed in Fig. 6, and those for vertical and horizontal vibrations have the same slope in the domain above 7 Hz. The ES curve of the vertical vibration in lying posture (Fig. 8) is lower by 11 dB than that of the horizontal vibration near 80 Hz. ES curves of the hand vibration are almost similar to those of the horizontal whole body vibration. Thus, by the value on these ES curves we define the vibration greatness level which has unit of VGL corresponding to the loudness level (phon). Next, the sensation difference between vertical and horizontal vibrations was observed. It is seen in the domain above 10 Hz that the sensation of the vertical vibration is severer by about 10 dB in sitting and by about 13 dB in standing posture than that of the horizontal vibration of the same amplitude. This difference gradually decreases below 10 Hz till it vanishes near 2 Hz, while there is no sensation difference between the two vibrations on the hand. Finally, correlation between the VGL values and unpleasant or intolerable level was defined as Eq. 1. This expression was determined by carrying out short time exposure experiments with 10 min. and referring to long exposure results in the draft of ISO/TC 108/WG 7.
1971-01-10

正弦振動の評価法 : 振動の評価法1

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