Evaluation of Whole-body Vibration on Comfort by Category Judgment Method

摘要

The purpose of this research is to establish a scale for comfort in the whole body vibration by Category Judgment Method. Random signals are used for the stimuli for the experiment, that consist of three kinds of signals with stimulus F which has flat PSD from 1to 100Hz, stimulus H with PSD which becomes 20 dB higher at 100 Hz than at 1 Hz, and stimulus L which has 20 dB lower PSD at 100Hz vice versa. These signals are modified by a frequency weighting of Wk based on ISO 2631-1, and the r.m.s. values were adjusted to be equal. Furthermore, the levels of the signals were varied with five steps to make 15 kinds of stimuli. These signals were used three times each and totally 45 stimuli were presented. The subjects sat on a flat horizontal metal plate mounted directly on the vibrator and were presented with vertical vibrations. Each vibration was presented randomly for 5s and a 2s pause separated the stimuli. The subjects were asked to judge a corresponding category number that was thought to be reflecting the comfortableness for each stimulus. Consequently, each continuous category showing the comfortableness on vibration and the frequency weighted r.m.s. acceleration was able to be connected. Moreover, it became clear that judgment changes according to the differences in the spectrum of vibration.