300 / 2021-04-22 16:08:55

Masking on Perception of Seated Human Exposed to Vertical Whole-body Vibration

Whole-body vibration,Seated human,Masking,Perception threshold

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Evaluations of the effects of whole-body vibration exposure on health, comfort, etc. are provided in ISO 2631-1. The evaluations of them are performed using index values. The index values are obtained by converting amplitude of the vibration that the humans are exposed using frequency weighting curves based on a human sensory. However, it is pointed out that the index values do not match with the sensation of automobile occupants. One of the reasons of the gap is considered to be a masking effect. The occupants are exposed to vibration including the resonances from an unsprung mass and other different sources. It is conceivable that the unsprung resonance which has large amplitude in 10 to 15 Hz acts as a masker and the masking makes the difference between the index values and the human sensory. In this study, vibration experiments of the human body are performed in order to examine the influence of the masking on the perception threshold for vertical vibration. Subjects seated on a rigid seat fixed on a shaking table. They were excited from the seat in the vertical direction in a sinusoidal vibration with a masker vibration. Masked threshold of sinusoidal vibration was measured at each frequency under the masker by up-down transformed response method (UDTR method). The masker vibration was the narrow-band random vibration from 10 to 15 Hz. And amplitudes of the masker were 0.1, 0.3 and 0.6 m/s² r.m.s.. Masking effects were confirmed. The masked thresholds especially around masker frequencies were higher than unmasked thresholds.