Predicting the subjective response to nonsteady vibration based on the summation of subjective magnitude

A purpose of this study was to determine the values of exponents of psychophysical functions for the discomfort produced by whole-body vertical vibration. In addition, the applicability of a method of predicting the average stimulus intensity of a stimulus the intensity of which varies with time was investigated. The first experiment investigated the effect on discomfort of the duration of vibration (for durations of 2, 5, 10, 20, and 50 s) and of the vibration acceleration magnitude [for 0.5, 0.75, 1.11, 1.67, and 2.5 ms-2 (rms) at 8 Hz]. The magnitude estimation method was used. The results show that the logarithm of the magnitude estimates is in linear proportion to both the logarithm of the acceleration and the logarithm of the duration. The values of exponents for acceleration and duration were 0.96 and 0.56, respectively. In the second experiment, the point of subjective equality of each of 16 nonsteady vibrations was measured and compared with the stimulus intensity predicted by means of the method proposed by the authors. Good agreement was found between the measured and predicted stimulus intensity and it was confirmed that the predicting method could be applied to vibration as well as to noise.