Difference thresholds for intensity perception of whole-body vertical vibration: Effect of frequency and magnitude

Abstract

EnglandRunning title: Whole-body vibration perceptionPublished as: Difference thresholds for intensity perception of whole-body vertical vibration: effect of frequency and magnitude Morioka, M. & Griffin, M. J. 2000 In : Journal of the Acoustical Society of America. 107, 1, p. 620-624.-2 - ABSTRACTDifference thresholds for seated subjects exposed to whole-body vertical sinusoidal vibration have been determined at two vibration magnitudes (0.1 and 0.5 ms -2 r.m.s.) and at two frequencies (5 and 20 Hz). For twelve subjects, difference thresholds were determined using the up-and-down transformed response method based on two-interval forced-choice tracking. At both frequencies, the difference thresholds increased by a factor of five when the magnitude of the vibration increased from 0.1 to 0.5 ms -2 r.m.s. The median relative difference thresholds, Weber fractions (ΔI/I), expressed as percentages, were about 10%and did not differ significantly between the two vibration magnitudes or the two frequencies.It is concluded that for the conditions investigated the difference thresholds for whole-body vibration are approximately consistent with Weber's Law. A vibration magnitude will need to be reduced by more than about 10% for the change to be detectable by human subjects; vibration measurements will be required to detect reductions of less than 10 %.

Influence of Frequency on Difference Thresholds for Magnitude of Vertical Sinusoidal Whole-Body Vibration.

“…In the previous studies of the difference thresholds by Morioka and Griffin 5) and Bellmann et al 6) , it was concluded that there was no frequency dependence of difference thresholds found. It was reported by Morioka and Griffin 5) that there was no statistically significant difference in the difference thresholds between the two vibration frequencies at the two vibration magnitudes used.…”

“…It was reported by Morioka and Griffin 5) that there was no statistically significant difference in the difference thresholds between the two vibration frequencies at the two vibration magnitudes used. Although there was a statistically significant difference between the difference thresholds obtained at frequencies of 4 and 16 Hz in this study, the frequencies used in Morioka and Griffin 5) , 5 and 20 Hz, were not used in this study so that discussion based Table 1.…”

“…Maeda and Griffin found that vibrotactile thresholds on the finger were influenced by psychometric methods that estimate positive responses at different probabilities 12) . Other factors, including the posture of subjects, the condition of footrest and backrest, the increment size for vibration magnitude, used in this study was similar to those used in Morioka and Griffin 5) , but different from those in Bellmann et al 6) . Therefore, the difference in the psychophysical method may have contributed to lower relative difference thresholds obtained in this study compared to those obtained in Morioka and Griffin 5) , while the causes of the differences in the relative thresholds observed between this study and Bellmann et al 6) could include various other factors.…”

“…The method used in this study may be categorized as the 'method of limits': if the response that a subject can detect the difference in the magnitude between the reference vibration and the test vibration is defined as the 'positive' response and this response follows a typical psychometric function, the method used in this study estimates difference thresholds at the probability of the positive response of 50% 11) . The two previous studies mentioned above used the up-and-down transformed response (UDTR) methods: Morioka and Griffin 5) used the method that estimates difference thresholds at 79.4% positive response and Bellmann et al 6) used the method that estimates difference thresholds at 70.7% positive response. Maeda and Griffin found that vibrotactile thresholds on the finger were influenced by psychometric methods that estimate positive responses at different probabilities 12) .…”

Discomfort from feeling vehicle vibration

“…Reductions of 5% or 10% in vibration magnitude are usually undetectable in subject ratings but, together with other similar changes, they are necessary for the optimisation of comfort [26]. The benefits of changes that are too small to be detected individually can be quantified using current methods of measuring and evaluating vibration.…”